Power Supply testing tools

Hey all,
I recently purchased a nVidia 7600 GS AGP card. It replaced a 6800 I had in one of my systems. I have a 350W power supply. I installed the new card and all was fine for a few days. I recently rebooted my box and the nVidia software popped up a window that indicated that the card was not receiving sufficient power and that it was going to disable features so as to avoid harming my system. I checked all power connections in the box and they all seemed seated just fine. I went out and purchased a 500W power supply and installed it. I am still getting the same error message. I have 3 harddrives, a DVD drive, the graphics card and a PCI based USB/Firewire card that directly draw power from the power supply. I am quiet surprised that I am still getting the error message. I'm going to do some further testing (i.e. disconnecting peripherals to see if the message goes away).

So I guess my questions are:
1. Is there any applications that report on the load of the power supply?
2. Do I have a defective graphics card?

Any help would be appreciated. Thanks in advance.
GT Smith

Additional note: I ran through the PSU calculator on this site and it calculated my requirements at 254 watts (I overloaded on a few things to be safe)

How many amps on the +12 volt line?
How old was your last PSU?
Who made your current and old PSU's?

None that you want to use.
Get a digital multimeter.

A possibility.

Thanks for all the replies. The old PSU is a MadDog 350W manufactured may 2005, the current one is a CompUSA unit. I disconnected my PCI USB/Firewire card and left everything else connected and I dont get the alarm any more. odd thing is I didn't even have anything connected to the card before, does it draw its full power even if no peripherals are connected?