Helping someone out who is having a problem. Computer has Win 7 Pro, fairly recent (last 2 years), reload of OS from disk, that I did.

Here's the problem:
Every so often the laptop will freeze, give the spinning circle and you can't do anything else. After a minute or two, it unfreezes and all is fine.

I was over there early last week and here is what I did to try to solve this:
Checked for unwanted new programs, updated and scanned with CCleaner, Malwarebytes Antimalware and MSE. Also looked thru all files and folders for junk and completely cleaned out any temp or temp internet file folders. I also tested the hard disk with a Boot Disk Test CD (GWSCAN) as well as having Windows do a scandisk on next bootup. Nothing was found and all should have been clean. In fact, I am like 99% certain this is not a virus or malware running on the laptop causing this. One other thing I did was update Firefox. I thought maybe a recnt update of Firefox introduced some kind of problem (like from a corrupt file or such). Before I left, the laptop seemed to be much better, but 2 days later he said it is doing the same thing.

Any ideas what else this might be?