How do you know if a power supply is compatible with your computer

[sourdruid]

Hello,
I have a compaq presario CQ5320 and im in need of a new power supply. I am planning on upgrading to a gtx 260.

 

[COLGeek]

That Compaq can use any standard ATX PSU. Its standard 250w PSU is not enough for a GTX 260 which requires a 500 PSU (see link below):

http://www.geforce.com/hardware/desktop-gpus/geforce-gtx-260/specifications

What is your budget for a new PSU?

 

[sourdruid]

Highest would be $100. Something that can run the 260 and is cheap would be preferred.