You can try measuring all the power supply legs to see if they are in spec but I've run across too many fried supplies as people install new cards but are disregarding the requirements on the PSU.
I recently tried to upgrade a new Graphics card in my Gateway 700XL. After inserting the card the PC will not power up properly. When the power button is pushed the button stay orange and never turns green. The only way to turn it off is to remove the power plug. I returned to the original configuration same problem. Next I removed the DVD, CD Writer, and diskette drive and removed all the PCI cards. Same problem. The original hardware configuraion is restored to how it was when it last worked. Same problem. It appears the mother board is getting power as there are two LEDS that are on. The power supply appears to be on etc.
Has anyone every come acroos this? Gateway support won't assist unless I open a fee based support call. The Desktop configuration is as follows:
Compaq 700XL on XP Pro with the latest SP and updates
I GB memory
100 GB Disk
16X DVD Player
3.5inch floppy diskette drive
Creative Audigy Sound Card, NetGear WPN311 Wifi card, and modem installed on PCI bus
GeForce Graphic card (AGP)