I'm building a gaming computer with the following parts:

Athlon 64 3000+ CPU
Socket 754 Motherboard
ATI Radeon 9800 Pro video card
1 GB DDR RAM
80 GB Hard Drive
DVD/CDROM Drive
Audigy 2 ZS

plus the CPU fan, motherboard fan, the the fan for the power supply.


I already own a computer case with a *generic* 300W power supply.
When I upgrade my PC with the parts I listed above, will the 300-Watt
power supply suffice? Or would that be a very bad idea?

The saleslady at the PC store I visited insisted that I'll need a
350-Watt power supply to go with all the other things I bought. I
told her I already had a 300-Watt power supply at home.