Power Supply

I have a computer with a bad power supply, this is a 400 watt PS. Out of curiousity could I test with a lower wattage PS just to make sure that is all that is wrong with the computer?

Computer model:
gateway gm5474

Power Supply Specs:

?100 – 127 V ~ /10 A
?200 – 240 V ~ /5 A

Frequency 50 Hz – 60 Hz
Output ?+12V1: 12 V / 16 A (max)
?+5V: +5 V / 14 A (max)
?+3.3V: 3.3 V / 20 A (max)
?+12V2: +12 V / 16 A (max)
?+5VSB: +5 V / 2.0 A (max)
?-12V: -12 V / 0.3 A (max)

Maximum Power 400 watts
Notes ?+5V and +3.3V output cannot exceed 140 watts.
?+12V and +12V2 combined current cannot exceed 30 A.

Thank You in advance for any input