winxp pro sp2
compaq presarioi sr1720NX
motherboard A8AE-LE AmberrineM

power supply with unit is 200W.

want to install new graphic card Nvidia 8600 serikes.
requires 350W PS.

Has a Coolmax V-500 (500W) picked up on black friday for 10.00.
Will this work?

Also want to increase memory from 512 MB (2x256) to 2 GB. (1x1GB)
will motherboard accept High density in pairs?
Or does ram have to be low density?

Computer is used mainly for Flight simulator with lots of planes.
Elderly Retired person. Main activity.