One thing before we go any further with setting the on access protection control, we need to check your computer's RAM and speed.
I am assuming you have Windows XP, so can you go to Start, and click your right mouse button on My Computer, then in the menu that comes up please click your left mouse button on the Properties link at the bottom, and tell us exactly what text you see in the dialogue box. We need to know everything it says next to Manufactured and supported by.
Sorry Technical if I'm butting in here, it just occurred to me that I read somewhere on the forum quite recently that some of the less powerful computers/operating systems are not happy if you set On Access Protection Control to High as it uses up too many resources.
Also which Service Pack does it say you have, Service Pack 1 or Service Pack 2.