For anyone struggling to get this game working (original retail DVD v2.0.0.) with similar hardware specifications to mine (see first post) and you are using Windows 7 64-bit that has only 64MB Dedicated Memory, then hopefully the following will work for you.
First, as mentioned in numerous topics here, install GTA: SA as Administrator and also ensure you have set Compatibility to Windows XP.
Now you need to downgrade Windows 7 and disable a few things:
Note: Please bear in mind that I would only advise to do what's listed below if you are desperate to get SA working! You will need to reverse all steps to revert your PC back to original settings.
A. Change your Windows 7 to Windows 7 Basic. Do this by right-clicking desktop and selecting Personalise > Windows 7 Basic.
B. Downgrade your computer further:
1. Start > Right-click Computer, select Advanced System Settings
2. Advanced tab > Click on Settings for Performance
3. Radio button - select Adjust for best performance. Click on Apply. This part may take a minute or so. Once done, click on OK.
C. Disable all desktop Gadgets by right-clicking desktop and selecting View > Show desktop gadgets
D. Disconnect from Internet then disable ALL security software as these run in the background and take up valuable resources (i.e. AVG, Norton, anti-spyware, etc, etc.)
E. Finally, locate gta_sa.exe on your PC and run as Administrator. Hopefully, your game will now load. You'll know if it is as the mouse pointer changes to animated CD image.
If you find the game lagging, right-click gta_sa.exe and select Properties then adjust Compatibility settings as necessary (i.e. Run in 640x480 resolution, 256 colours, etc.)
If anyone else knows of a quicker way other than the above to "downgrade" computer then please let us know.
btw, I couldn't tell you if the above would work for other GTA games as I don't have them but would imagine they should.
I have experienced the same scenario as you. I tried this, but no success.