Yep, you can take a look at native auditing but this way if Im not wrong you should look through server event log. It's really boring and wasting time.
But Im sure there are some 3rd party solutions that can solve this issue...
I don't remember the particular names - google will help...
It depends on files...
Of course, it's better to reinstall XP one more.
If you have another CD-Rom drive - it's better to do it using it. But also your XP CD may be damaged.
Some applications may cause wake up difficulties. You can try to make a test by leaving your PC alone for along time when particular programs are running and you can see what will happen. Also wake up issues may be caused by some hardware troubles, for example with videocard. Try to update video...