Not a problem.

But after removing all the stuff below the uninstall entry in Control Panel .. Programs, the MariaDB 5.2 entry disappeared.

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Installer\UserData\S-1-5-21-2656319016-1596626723-3555400582-1000\Products\3DC5D27742DD8714EA85F2707228779F]

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Installer\UserData\S-1-5-21-2656319016-1596626723-3555400582-1000\Products\3DC5D27742DD8714EA85F2707228779F\Features]
"Client"="*V!x7(bawA0V)$m@+GB,{WY~*^C8qCrM')aqrC,29R`LXpATUDPXFt6c[N$'TXF?,C.EmC?E4`e.Hn.x4O.Ry,as7E*i948Dda$7C0hvfcbcDDYV6E=%M0^98b!2AwYq!EFTx$rkR(Lxqx&wB6vAYD@XtU,1PB^UO5SXVz'nWFFjJLmKTU8F6yfa[RH_qDDk8-L'l=BYBWkO=MbKRBbJMAkrpn}dIMa75m!GDFRMhWu&vgG,!DbF_!O70BJ.H*[b]i`'4f^NNG^JMFbsK5=WW0EY._RUzU=*GFwF-8+Dfk%dF!-,fk0HaC-9BcU}2x!CEd9t%{&{[BJ0yg=sOFT'rw+oj!IG$DnQfH.J(*Bp9DBq1+8AEEi-?g+Wh8Iv MYSQLSERVER"
"MYSQLSERVER"="aESvqE3y)F[`1wE7m-B(ED~2{x)i@D=qfBgOlK~=Y4u2`m1%-CA}tHMxeV-'({LqA_6j?BMJm)WP0b=0Mz=x&!%b@EM)'+&cZKGvybVoK`$xqD-,NQKdS(GXHv7v?54[SDa=`vrc!?x+*EzvG%?UFD%la}`K]p+JU24u$!To*C0n?n'c_z6*GRyqG_HY!DO-WDFS*6p9Uf~C^!cYxB'86ALM1ahxFP`nr0^tVEXnO1wo_7sxl&o(mjP,uBa(Ili-Cr4xpo,r-+ocXB_.Uv6eKkCY=UAyXFXD)D.`a-WPZE[wtaz5S5YE3Ei7hmf*t]['AQe=)kNaUC`W5c_)YBtmEbP%^P4sZF^X!rL4YCE^'KPel?cK?CW_Fj.Ne}]aTXQU)s@*tE7AIsNam}PDQNSA_38olB`3j8_K48,M9Z2qa3i.LD63TiecY]9peKh4r,T@eF^fz_UoVu-mP+g21p$ZLBV}d(`Y2FP31N,ym0MO9D-7SYDVzeV,uvcZ[?0vxAdat5T+LMoQ%'m8Lup=dCxxsZ3[4l%i*[HU4HldzC6SYvO!_Koxq3W0FMIjaBg[COTXZgV!Ij5P%A1T7CcvGoUcN'LeGA997arUzBv?^]$-2I*8Ymade]{t{BvRp3h8eGl@J}=zhm68BFs-iXQp6J7tr(+Q'D[snBtDbn3G*E+ZyR~1{N}HOCNAdVhCEba&bdzE2&ui2FbYQ^E(jW@WWXr0``SLiB]C9wr-OsjcG)8UEVkVUF36ADH6cg-V3C-~o0%?0E)YQ?YJNe]MPhE!L}qa,FYAt,`8yE[=1zqbL'1t{EZKo,1&p1]swU2!HsvSmF=ga%abh*Re9lIH@CI[*EPIu4Vo@HtR)Y6xkZiWzA@wgBFv2btr@'AV%hpEjC-DlG^`+}2fdQq4ybg9aFp3_'C=SzeNTqo[`~j9`C^S`^LUSVe*6j(!B06soACumN?Q-}Yb~dt6NmPOmA!Ujgwn6QFs?WgO^&a~2BpB[b^0vJV(0%u{uH*blFrSNx%hg6vg4NwV=Kl4cB]v!4RQpuF-+PK.ZoOO8DD4!gdB{BcKff)dkZ$poC[Bl$wzud.EvW3DD2V_9Bjo^mWfB3io=w5a9NG0hF.&2u)we}Gw?.DuJ*tV!DNCH[A1_+5F=XF^Q'lrLCgnis.L.pFr$0[zD$`RrD{u(CB1B-]-)S!`@!}rWB0]goSuHx=aNlkM(e4xLEja1%B(!Q'$E9A03Z'w2CoH$*U&7a2_Ts0&p$~YsA(vMG)a!bT9c`2N,%+{{Elm`V&vC}!7uH%mJ+EsTFYQs[&sX{eKpXVbvbdXrDNip^%${a!60_{z9$6gtDd9)Fit[mWu!@S!+Z_]ZC@@b!O$5]lk{6Oq^$1o.C)XuM.lpusFw^Qu4?VR=B.}G7ukFtbM"
"SharedLibraries"="!VvGRUhA7D}G&hpvlOAPk^_*pH'u^Bl_WScKT}Tv DEVEL"
"DEVEL"="g2y`gk{M_D$Km+(==`*bNiu^kc-WjDh$Yx4tc,jE`jlwv]c%SDocM0dV7p{Ob0G=PSFsKE,cfuo}dftz)XX)9FyyiF.U]fhLvYOIlPBTo8u9oCtcE.J`aYz)^b}T3TvHpAof{1?3y7TwZsFtRmJD7FeROtyl_OKSb}(D*@o9DCA2]fq,}D@VL1(ChTlb8CL0KwZ`~0.ZR-uWpKHXBD{oGw-U=0[Xx~k0e[A4REP3`FWIf1gtgB}G*fS[$D'[A(3WO!hTz^!7Ts-P%CS`tfpvy=9ZtDVw3f9(vE**$p_a0oort5M+eI3WQCStuFFGUO'MNM^sv[O4rD]Io)o,KTNSu{LYJ[AgFC48=uau9!.G-BM17g]3SB_h!u,Ulzu&=Q?inRyP{CY9v1Xw7s}gCRy.`inIcE]8d8fO-^vgAvkkp{[ydB+Z.o'Am14Qew*'R4&=GD8C4(oynJiWul=pHy*)SF}HZ0b~k3eN~1f'4rkZZFFT6ROLwDlmpW'M&(d5xADd'0mDu@qNKH-e)Qih~CCe==Q?~-r2^iA4+`}jWCfn.*ru$rzk[]Lo-Viv^DQsyyUUj)5*7Y'IWlugkCQbBe)4dm[Hq25E^Yx4`F*oCupqJLAUzQWo?b&%wD}QDLK[*?v2kkMnJIq8oEAi6)xZa0&@E3r6rO{}qBj8FQ7lUW&1%zczKFLb&C(}i[xI`(FSdn4QLiVPyBTT4Soi1CB2Z+ngohfh,Ex%nrMJ[^-@Cz?ax'(D.CK(ZozfPZjo!o12iP{-yAS`f=HuM!D$ZYr9ktjTlFSS]0@IvEQ.`?hO4X^pEF*,jST0%K8?NV(aVT^%TFOZtwm[0gyIHzc_F=5nhD-AZv?@qB?5"
"IniFiles"="y!eaH~IHnEEWG%iEA,fiCDPvP&(={Aq7oEu,D6oChd,hG=UoPC}Ppj]w(&`p(_b6F`2qxBZ^Jsa.A.=P MISC"
"MISC"=""
"Server_Scripts"="sUdatcgZ3B9I@RvU-mtR[2DrNHFN+D&LN`DIb%7D0f.3h_{eSE!1E}ED-pC.GZ.alSgVaB$)uaFkKx]O?sI{*dr8(EZ']%@eFJO*ZWWI$R-cqEBT'bXlES2ts%$@7V*.2EHB$7pZApA7 MISC"
"Readme"="C`Z`LxTsEBjuq1mfC]9SISx7ZqT%&DF}4zJP?C~s ALWAYSINSTALL"
"ALWAYSINSTALL"=""
"DBInstance"="6yfa[RH_qDDk8-L'l=BY_*nn[)r98B_]Qkt=ty$LFHzHifpZrD-FI+tl%`)F?%y+!zoEXDapeca9~.+X}I3Byrr!}AVbz8pk_QhU(Ps8Dlcw'E=g_E!WK{(wiv4$qCj6oBMp$HfgiYO^ MYSQLSERVER"
"SharedClientServerComponents"="6yfa[RH_qDDk8-L'l=BYBWkO=MbKRBbJMAkrpn}d!DbF_!O70BJ.H*[b]i`'9DBq1+8AEEi-?g+Wh8Iv5`aU(_jg2FNdm)0l.^_r MYSQLSERVER"
"StoreInstallLocation"=".I7}]L{[lCZmgkt=4[F*"
"ARPRegistryEntries"="B)dba*=vPD[l+V5z9Vx("

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Installer\UserData\S-1-5-21-2656319016-1596626723-3555400582-1000\Products\3DC5D27742DD8714EA85F2707228779F\InstallProperties]
"LocalPackage"="C:\\Windows\\Installer\\f9375b0.msi"
"AuthorizedCDFPrefix"=""
"Comments"=""
"Contact"=""
"DisplayVersion"="5.2.5"
"HelpLink"=""
"HelpTelephone"=""
"InstallDate"="20110202"
"InstallLocation"="C:\\Program Files\\MariaDB 5.2\\"
"InstallSource"="C:\\Users\\Peter\\Desktop\\"
"ModifyPath"=hex(2):4d,00,73,00,69,00,45,00,78,00,65,00,63,00,2e,00,65,00,78,\
00,65,00,20,00,2f,00,49,00,7b,00,37,00,37,00,32,00,44,00,35,00,43,00,44,00,\
33,00,2d,00,44,00,44,00,32,00,34,00,2d,00,34,00,31,00,37,00,38,00,2d,00,41,\
00,45,00,35,00,38,00,2d,00,32,00,46,00,30,00,37,00,32,00,37,00,38,00,32,00,\
37,00,37,00,46,00,39,00,7d,00,00,00
"Publisher"="Monty Program AB"
"Readme"=""
"Size"=""
"EstimatedSize"=dword:0001b978
"SystemComponent"=dword:00000001
"UninstallString"=hex(2):4d,00,73,00,69,00,45,00,78,00,65,00,63,00,2e,00,65,00,\
78,00,65,00,20,00,2f,00,49,00,7b,00,37,00,37,00,32,00,44,00,35,00,43,00,44,\
00,33,00,2d,00,44,00,44,00,32,00,34,00,2d,00,34,00,31,00,37,00,38,00,2d,00,\
41,00,45,00,35,00,38,00,2d,00,32,00,46,00,30,00,37,00,32,00,37,00,38,00,32,\
00,37,00,37,00,46,00,39,00,7d,00,00,00
"URLInfoAbout"=""
"URLUpdateInfo"=""
"VersionMajor"=dword:00000005
"VersionMinor"=dword:00000002
"WindowsInstaller"=dword:00000001
"Version"=dword:05020005
"Language"=dword:00000409
"DisplayName"="MariaDB 5.2 (x64)"

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Installer\UserData\S-1-5-21-2656319016-1596626723-3555400582-1000\Products\3DC5D27742DD8714EA85F2707228779F\Patches]
"AllPatches"=""

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Installer\UserData\S-1-5-21-2656319016-1596626723-3555400582-1000\Products\3DC5D27742DD8714EA85F2707228779F\Usage]

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{772D5CD3-DD24-4178-AE58-2F07278277F9}]
"AuthorizedCDFPrefix"=""
"Comments"=""
"Contact"=""
"DisplayVersion"="5.2.5"
"HelpLink"=""
"HelpTelephone"=""
"InstallDate"="20110202"
"InstallLocation"="C:\\Program Files\\MariaDB 5.2\\"
"InstallSource"="C:\\Users\\Peter\\Desktop\\"
"ModifyPath"=hex(2):4d,00,73,00,69,00,45,00,78,00,65,00,63,00,2e,00,65,00,78,\
00,65,00,20,00,2f,00,49,00,7b,00,37,00,37,00,32,00,44,00,35,00,43,00,44,00,\
33,00,2d,00,44,00,44,00,32,00,34,00,2d,00,34,00,31,00,37,00,38,00,2d,00,41,\
00,45,00,35,00,38,00,2d,00,32,00,46,00,30,00,37,00,32,00,37,00,38,00,32,00,\
37,00,37,00,46,00,39,00,7d,00,00,00
"Publisher"="Monty Program AB"
"Readme"=""
"Size"=""
"EstimatedSize"=dword:0001b978
"SystemComponent"=dword:00000001
"UninstallString"=hex(2):4d,00,73,00,69,00,45,00,78,00,65,00,63,00,2e,00,65,00,\
78,00,65,00,20,00,2f,00,49,00,7b,00,37,00,37,00,32,00,44,00,35,00,43,00,44,\
00,33,00,2d,00,44,00,44,00,32,00,34,00,2d,00,34,00,31,00,37,00,38,00,2d,00,\
41,00,45,00,35,00,38,00,2d,00,32,00,46,00,30,00,37,00,32,00,37,00,38,00,32,\
00,37,00,37,00,46,00,39,00,7d,00,00,00
"URLInfoAbout"=""
"URLUpdateInfo"=""
"VersionMajor"=dword:00000005
"VersionMinor"=dword:00000002
"WindowsInstaller"=dword:00000001
"Version"=dword:05020005
"Language"=dword:00000409
"DisplayName"="MariaDB 5.2 (x64)"

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\MariaDB 5.2 (x64)]
"DisplayName"="MariaDB 5.2 (x64)"
"Publisher"="Monty Program AB"
"DisplayVersion"="5.2.10"
"InstallLocation"="C:\\Program Files\\MariaDB 5.2\\"
"UninstallString"="msiexec.exe /I {6EB56EF1-B9A9-431D-995F-EE4840481210}"
"MajorVersion"="5"
"MinorVersion"="2"

[HKEY_LOCAL_MACHINE\SOFTWARE\Monty Program AB\MariaDB 5.2 (x64)]
"SERVICENAME"="maria52"
"servicepermission"="1"
"INSTALLDIR"="C:\\Program Files\\MariaDB 5.2\\"

[HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\maria52]
"Type"=dword:00000010
"Start"=dword:00000003
"ErrorControl"=dword:00000001
"ImagePath"=hex(2):22,00,43,00,3a,00,5c,00,50,00,72,00,6f,00,67,00,72,00,61,00,\
6d,00,20,00,46,00,69,00,6c,00,65,00,73,00,5c,00,4d,00,61,00,72,00,69,00,61,\
00,44,00,42,00,20,00,35,00,2e,00,32,00,5c,00,62,00,69,00,6e,00,5c,00,6d,00,\
79,00,73,00,71,00,6c,00,64,00,2e,00,65,00,78,00,65,00,22,00,20,00,22,00,2d,\
00,2d,00,64,00,65,00,66,00,61,00,75,00,6c,00,74,00,73,00,2d,00,66,00,69,00,\
6c,00,65,00,3d,00,43,00,3a,00,5c,00,50,00,72,00,6f,00,67,00,72,00,61,00,6d,\
00,20,00,46,00,69,00,6c,00,65,00,73,00,5c,00,4d,00,61,00,72,00,69,00,61,00,\
44,00,42,00,20,00,35,00,2e,00,32,00,5c,00,64,00,61,00,74,00,61,00,5c,00,6d,\
00,79,00,2e,00,69,00,6e,00,69,00,22,00,20,00,22,00,6d,00,61,00,72,00,69,00,\
61,00,35,00,32,00,22,00,00,00
"DisplayName"="maria52"
"ObjectName"="NT AUTHORITY\\NetworkService"
"Description"="MariaDB database server"

[HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\services\maria52]
"Type"=dword:00000010
"Start"=dword:00000003
"ErrorControl"=dword:00000001
"ImagePath"=hex(2):22,00,43,00,3a,00,5c,00,50,00,72,00,6f,00,67,00,72,00,61,00,\
6d,00,20,00,46,00,69,00,6c,00,65,00,73,00,5c,00,4d,00,61,00,72,00,69,00,61,\
00,44,00,42,00,20,00,35,00,2e,00,32,00,5c,00,62,00,69,00,6e,00,5c,00,6d,00,\
79,00,73,00,71,00,6c,00,64,00,2e,00,65,00,78,00,65,00,22,00,20,00,22,00,2d,\
00,2d,00,64,00,65,00,66,00,61,00,75,00,6c,00,74,00,73,00,2d,00,66,00,69,00,\
6c,00,65,00,3d,00,43,00,3a,00,5c,00,50,00,72,00,6f,00,67,00,72,00,61,00,6d,\
00,20,00,46,00,69,00,6c,00,65,00,73,00,5c,00,4d,00,61,00,72,00,69,00,61,00,\
44,00,42,00,20,00,35,00,2e,00,32,00,5c,00,64,00,61,00,74,00,61,00,5c,00,6d,\
00,79,00,2e,00,69,00,6e,00,69,00,22,00,20,00,22,00,6d,00,61,00,72,00,69,00,\
61,00,35,00,32,00,22,00,00,00
"DisplayName"="maria52"
"ObjectName"="NT AUTHORITY\\NetworkService"
"Description"="MariaDB database server"

There could be an issue with my system.  But it would have been nice with some advice on how I could remove the entry (which of the ones above that matters, for instance).

Still you did not reply to why my registry had entries like the mysql.h file.  I removed more than hundred of those. Some are are files that never existed on my system (I never had the soruce code, as I don't know what to do with it). Do you have files registered in Visual Studio and add registry entries file from your system on users' systems? Anyway this is not a real problem. The only real problem that the uninstall con in CÅ .. Programs did not go with the uninstallation.

Also I may have had older 5.2 versions before 5.2.10 (the last 5.2 I had) installed and some of the garbage in registry may have come from such older version(s). I also found a little left-over garbage from 5.3 (that was uninstalled a few months ago), but only few percent of what was left over from 5.2.

All this was mainly posted FYI, BTW. I can handle such issues on my system. But you should know what to reply to users reporting this in the future - if it should happen again.

-- Peter