Yeah, I forgot to mention that "System Restore" won't be on some older versions of Windows (such as 95, 98). But as far as I know it is on ME, 2000, NT and XP.
System Restore points are usually created automatically from time to time, so if you're still having troubles it might be worth a try, but if you don't have confidence in trying that then you will need to try and figure out what is causing your problems. There's been a few times before when my computer was messed up and I wasn't able to track down what was the cause of the problems and doing a System Restore fixed the problems.
Perhaps try running AGS from "Safe Mode". You can usually get into safe mode by tapping the "F8" key on starting up the computer and before Windows starts loading in, which should bring up a "boot menu" and having Safe Mode as one of the boot-up options.
If AGS does run ok in safe mode, then chances are some other program, drivers or application that would normally load in may be causing some conflict preventing it from running properly.
Another thing to try could be to re-install AGS but into a new/different directory. Maybe for some strange reason the current directory in which the AGS program resides on your computer is messed up somehow?
You might also consider installing the most recent version of drivers for your graphic and sound cards and/or installing the most recent verison of DirectX, but not knowing what the cause of the problem is, that may or may not help.