*Some background info: This computer is a VAIO RA825G. I bought it refurbished off of Ebay in the fall of 2005. I kept the stock ATI X300 in for a while but installed a Nvidia 6800 GT by BFG(the overclocked out of the box model) and had that card running fine for at least a year. The power supply of my computer at the time was the stock Sony 363 Watt one which was probably a little weak for that card and may have contributed to the power supply giving out. Around November of last year the harddrive gave out which makes me believe poor quality components were used in the refurbishing process throughout. The processor has a metal tube water cooling system as well. The power supply I replaced my old one with was a mini ATX as that is all that would fit, my previous power supply was not a mini ATX however. I don't know if the form factor would make a difference. So about a few months ago I heard a pop from the back of my computer and the smell of smoke. I wasn't positive on what the problem was but I suspected it was a power supply burn out. I then ordered some cheap $20 450 Watt Chinese power supply off ebay as I was short on money and had it working fine for a month for the most part. The only issue was that initially my computer would crash whenever I ran something such as a graphics intensive game. I later found out with a temperature program (SpeedFan) that the case, graphics card, and cpu temperature ran around 70 Celsius normally and shot up to 90 Celsius until crashing when a game was run. I then took the power supply from the case and kept it outside while keeping the case open and running a fan through the whole thing. I got the temperature down to about 50 Celsius for normal running and at about 60 Celsius for gaming. Everything worked fine for a while. I then got overheat issues again and switched out my 6800 gt card for the old X300. After that as the CPU was at 50 Celsius about and maybe 60 Celsius for games and everything worked fine for a while. That's when things got weird. After running a game on it what seemed to happen was another overheat but the computer did not start again when I tried to turn it on. After trying various things I found that if i unplugged the power supply, switched it from 115V to 225v plugged it in again (it's a switching power supply), unplugged it, switched it to 115V again, and plugged it in, the computer would turn on fine. This didn't last long, after an hour it crashed again and would start up for only seconds with the above method. I then tried running on as low a power draw as possible by disconnecting a harddrive and the cd drives. This worked for a few hours until another crash happened that actually caused a loud popping noise like the first time my other power supply failed. I then tested the power supply with my cheap tester which just has one LED light which indicates if it works or not and apparently it still works. I then tried hooking it back up to the system but it only starts the system for a short while before crashing again. And like before it crashed immediately when I hook up another harddrive or cd drive. So I don't know what to do, the problem could be on the motherboard or with the power supply and I don't know what type of power supply I should get; higher wattage if the power supply failed because it was too weak or lower wattage if it failed because of overheating. Since the power supply tester said the power supply was working after the popping noise, maybe my other supply didn't actually break, though I threw it out so I'll never know. The problem may be something else altogether. Maybe dust behind the motherboard is causing some issues? Any input would be helpful, thanks.