Hi brokencrow,

There really isn't any hard and fast rule is there? What I do is pretty much a judgment call based on experience and things like noises, smells, lags etc.

Incidentally, there is a new release of memtest 86 (February 2009) which I think is the first in almost 2 years?

http://www.memtest86.com/download.html

Whilst you are at it you might have a look at this newer version called Memtest 86+ ("Advanced Memtest")

http://www.memtest.org/

There is even an M$ tool:

http://oca.microsoft.com/en/windiag.asp

I just thought I would mention it as I frequently find that HDD and RAM problems are pretty interchangeable as culprits