1. Clean it. CNET shows how at http://reviews.cnet.com/4520-11319_7-6240575-1.html
2. Take Grif's advice at 7726-6132_102-5098912.html?tag=posts;msg5099421
Second opinion scans are a good thing (I use that advice!)
I have a Dell Inspiron E1505 laptop with Vista Home Basic(yes, I know this is the pits). Recently when I turn my computer on, I can use it for a short while and then it freezes and the cursor will not move. Occasionally if I wait long enough it will spontaneously unfreeze but most times I have to turn the computer off by pressing the start button and then re-boot. This may happen several times and then finally I can proceed without it freezing. It almost seems like it takes time to warm up or something.
I empty my "prefetch" and %temp% files daily but that does not seem to make any difference.