When you uninstalled the game did you use the Game's own Uninstall feature or a third party?
Are all the Modding Folders Gone?
Are you playing the game in Vista/Win7 using
W98 (or XP) compatibility mode,
with Administrative Privileges?
1) Uninstall SA.
2) Delete the installation folder if it still exists. (e.g. C:\Program Files\Rockstar Games\GTA San Andreas).
3) Delete the Virtual Store copy of the installation folder too. The Appdata folder might be hidden. (e.g. C:\Users\???\AppData\Local\VirtualStore\Program Files\Rockstar Games\GTA San Andreas).
4) Delete the gta_sa.set file from your user files folder.
5) Reboot.
6) Reinstall SA.
To Unhide Folders:
START > User > Control Panel > Appearance and Personalization > Folder Options> Show Hidden files and Folders.
Adding to above and if you did that and it doesn't work, try going on this folder:
C:\Users\youruser\AppData\Local\VirtualStore\Program Files (x86 if it's 64bit OS)
and delete the Rockstar Games folder. Sometimes when the game crashes, Windows saves segments of files to that folder for troubleshooting and the game sometimes loads from there anyway.
