-I believe it's something to do with your hardware, or maybe i'm wrong; probably you should upgrade certain parts in your PC, such as your RAM, video card or processor.
-If not, I'd recommend you to analyzes your PC
here. This site is safe and it basically checks your computer's hardware and determine if you'd be able to run a certain game; it also tells you what needs to be updated in-order to play the game properly. It's free, you'd only have to install plug-in. When you're on the site, type in 'grand theft auto san andreas' and you should get a match. Or use
this link to start the analyzer automatically.
-You can try turning down your graphics settings to low;
- When you are in-game, press ESC
- Click options »» display settings »» Advanced
- Turn off Frame Limiter - Set Visual FQ Quality to low - Turn Anti Aliasing off - Drop the resolution to the lowest (Or play around with it)
- Once all of the settings were applied, press ESC until you get back into the game and test the perfomance.
If nothing works....;
- Closing background programs when playing,
- Set GTA/SAMP to run as administrator
- Set GTA/SAMP to a higher priority via task manger (may/ may not make a difference)
- Scan your computer with a highly recommended anti-virus
- Re-install windows & drivers
- GL!