Question : Problem: How can I tell what size power supply I need?

We have a

Visionman Vista Ultimate Intel Gaming PC - Intel Core 2 Duo E6550, 2GB DDR2, 250GB SATA-II 20X DL DVD±RW w/Lightscribe, NVIDIA GeForce 8800GT 512MB, Gigabit LAN, Windows Vista Ultimate MPN:  CC65-VGS

purchased in 6/2007.

It will no longer power up, although the case fans spin and blue leds flash briefly every 10 seconds or so.  I assume we need a new power supply - what would be a good size for this system so that it is not pushing the power supply to its limit.  Thank you.

Answer : Problem: How can I tell what size power supply I need?

NVidia recommends a minimum of 400W for that card.  A 450W should work, but for gaming PCs, especially ones running high-end video cards, it's never a bad idea to get a bigger power supply.  I would look at 600W and 700W.  Both should be more than fine... so I'd look at pricing on 600/700.