1. Get a program to fix your pc errors, CCleaner or Registry Fix are suggested for you now.
2. Remove GTA: SA & SA-MP Completely !!! Even clean the GTA SA... Start>Run>"regedit", browse HKEY_CURRENT_USER>Software, you will see the GTA Folders in there... Right Click > DELETE THEM!
3. Reboot the PC.
4. Re-Install GTA:SA & SA-MP..
Good Luck