memory isn't just something that you can switch around even if it's the same kind aka, ddr, ddr2, ddr3 etc. the speeds and case latency, their MB capacity, and a few other things play a role also. you'd have to find a ram that is everything the same basically. some motherboards will not support anything other than one type and maybe 2-3 different speeds. and since there are so many different designs of motherboards, no 2 computers will behave the same way. so it's impossible for anyone on the net to tell you for sure what the problem is. the other guys have already mentioned only a few out of probably a dozen things that are often associated with that, 1. ram 2. windows problem 3. cmos battery 4. hard drive failure 5. CPU failure 6. video card failure or not seated all the way there are many more but the chances become less likely. out of that list I would put 4 at the top and then 1.