you should always have two versions of GTA if you mod it, a vanilla one(for backup) and your modded version, so the best thing you can do is uninstall your current San Andreas and than install san andreas twice and call one San Andreas Vanilla , and you can call the other one the same as it is now if its on the XP, if you are on Vista or 7 call the second one something else aswell because if you have rebuilded the gta3.img file than it wont uninstall that file so it will just stay moded, or you can install it in the same folder if you will rebuild your img archives from the vanilla version to the moded version, but the easyest thing to do is just simply install it as "GTA San Andreas 2"