I have two computers with ANTEC 370W power supplies. Both are very quiet. 90W is VERY little power for a PC these days. Power draw for common Maxtor hard disk is on the order of 12W. Older, slower disks draw less power.

Hard disks contribute a lot to the noise in a computer too. My PC cases (Antec Sonata) mount all hard disks with rubber grommets to isolate them from the case.

I have my DAW built into a Sonata case with 4 hard disks. I have a Zalman heatsink on the CPU, a 120mm fan pulling air over the hard disks, a 120mm case fan blowing air out the back, and a 120mm fan blowing on the CPU heatsink. All fans are ANTEC and are controlled with Zalman Fanmates.

It is quiet enough that I record in the same room with the computer. I do use some pads to block what little noise it produces, but for a P4 2.4 it ain't bad. Uncle DaveO's CD was recorded in these conditions. I dare you to find computer noise on his recording ;)

karl
www.cheap-tracks.com