Listen to svdl about this temperature setting!!!

I burned my motherboard up doing a Maya dynamics render - when I opened the case, I had Dust Rhinos wrapped around the heat sink.  One moment to use compressed air ($10 can) would have saved me many hundreds of dollars.

Another thing I do with memory is settings on Virtual Memory for the machine.  I like to set it double the amount of RAM i have in both minimun and maximums.   (example - 1GB RAM, virtual memory 2GB)  and make sure you aways have 2GB space.

Check for virus.  Try CCleaner program (free) for general maintainence.   Clear out old renders from cache, and also consider clearing Undo cache as well (like right after a filesave)