The freezing sounds like it's one of the components are bad. You need to do some testing of components that you can test. You said you increased your RAM to 2GB, Did you buy all new memory or did you add additional to your existing memory? Here's what components I believe could be causing the problem. It's either the memory, cpu, or possibly the hard drive (that is easy to test) Just run a chkdsk from cmd prompt and if it comes clean, then it's not the disk. The last component which is not typically the problem (but can be) is the motherboard itself could have a short. It's not software, or any virus, since you've restored, upgraded, an the like, that usually will wipe any viruses out. I for some reason get the feeling it's the CPU. You said it started from out of the box, and it's been randomly doing this for a couple of years. (your are a very patient person) I would test the CPU HERE
s a free cpu tester. If it freezes during the test, then I'd say it's the cpu. If not then you need to start testing each componeant to make sure it's first a compatible part, and 2nd if it's in perfect working order.
Let me know how it goes.