these machines originally shipped with a sub 200 watt power supply. they were garbage.
upgraded to 350 watt ones, haven't had nearly as much issues. (just fans seizing up)
problem is mainly that the 175 or 200 or whatever...basically all power supplies, derate 10% at as little as 50 degrees celsius...these machines run that least hot. This means your 200 watt power supply is only pushing 180 watts....and your original 175 supply is only about 150 - probably less because those buggers run HOOOOOT. I opened one up one time and the main switchers heatsink was over 100 degrees celsius. I'll bet that supply only put out 75 watts by then.
a bigger supply 300 watts + won't work as hard to power the system, won't put out as much heat, and won't derate (as much) because of heat.
order from newegg or Ebay by searching "FLEX ATX Power supply". get an "80plus" rated supply, silver or gold if you can afford it. The 80plus rating means its more efficient (at least 80%) at converting the volts from the wall to usable power... 100 watts in, at least 80 watts out.
another warning....don't go all crazy and order a 1000 watt power supply. power supplies are inefficient when run way UNDER their rated load. you want about 25% overhead. any less, you actually waste power because the power supply has to work harder to regulate the tiny load on it's rails. this goes for desktop computers as well. The huge supply is expecting 35 amps of load on it's 3.3v rail and it only has 8, so the voltage fluctuates all over the place and the supply has to work extra hard to regulate that voltage cause it's basically no-load.