speaking of PSU's, i used to use the "generic" 400w p4 dynamo power supply (i think that's the 995pesos one from PC express) ... had it for about 5-6 months then the weirdest things happened... it would suddenly close. as if someone pulled the plug.
at first i wasn't sure what was the problem... but i had narrowed it down to either the MOBO or the PSU. i don't run a "fully-loaded" system... athlon64 2800+, 2 optical drives, 1 HDD, 1 floppy and 3 120mm (1-in, 2-out) fans. i do, however leave the PC running for long periods of time.
with that in mind i decided to get a new PSU, i got a TASK 450w dual fan PSU and so far so good. i also installed an additional fan for intake and switched to rounded cables for better airflow ... now, i can leave my PC on for 24 hours and still retain a sub 40degree machine. i'm a happy camper now.
my advice... ditch the generic PSU and get a branded one... they may be pricey but definitely worth the price.
p.s. i also installed "filters" on each of the CPU fans to keep at least some of the dirt out. my HDD also has "cooler fans" to keep it from overheating.