55 seems a bit high for a CPU running at stock, what kind of CPU do you have?
If you know your PSU is that iffy then you should indeed replace it with at *least* a good name-brand 350 watt job, preferably 450 watt. If you can't afford name-brand then go at least a generic 500 watt PSU.
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<b>Radeon <font color=red>9700 PRO</b></font color=red> <i>(o/c 332/345)</i>
<b>AthlonXP <font color=red>3200+</b></font color=red> <i>(Barton 2500+ o/c 400 FSB)</i>
<b>3dMark03: <font color=red>5,354</b>