Ok, I'm at a complete loss for how to trouble-shoot my system. I'm on the verge of pitching out the window, though I live on the ground floor so I'm afraid it won't do as much damage as I would like. I was running a Athlon XP 1800 on a K7S5A mobo with 2 sticks of 256 MB of PC133 RAM and an A+ 400 Watt power supply. I was getting frequent lock-ups during games, and the feedback I got at the time was that the K7S5A sometimes will do that as result of having 2 sticks instead of just one. Fine. I figured if I'm gonna upgrade the memory, I may as well get the faster stuff, so I orderd at 512 MB of PC2100 Crucial RAM. At the same time, I decided to get a new case which came with it's own power supply (which is identical to the one I had in my old case - same make and model, etc). Well, I put the new RAM in, transferred everything to the new case and fired it up. Except nothing happened. I don't mean it didn't post. I mean nothing happened at all. When I press the power button, the computer does the same thing it would if it wasn't plugged into the wall. Absolutely nothing happened. Well, since then I have tried virtually everything I can think of. Tried using the old power supply, made sure the power switch on it was set to I and not 0, made sure it was on 115 V, put everything back in the old case, swapped in different DDR RAM, swapped out the CMOS battery, reset the CMOS, tried an MSI mobo. Pretty much everything except swapping out the CPU. Does anyone have any idea what might be the problem? I'm about to have a nervous breakdown.