New video card causes pc to reboot

[jayajean]

I use Windows XP service pack 2 and currently have an SIS 760series video card on my motherboard.  I want to use a new program called Plan 3D but my card was not supported so I bought a new one.  It is a PCI NVidia GE force 5500 and when I installed it and started my computer up, it would run for 15sec. then restart.  It kept repeating this over and over, and I would get and error message saying System is recovering from a serious error.  When I plugged the monitor into the old port, it was fine.
Can you tell me what might be wrong?

[patio]

Not enough power ? ?
Describe your system components and what wattage your PSU is...

[jayajean]

The computer is an ACPI Uniprocessor pc, plug and play monitor, amd sempron 2400+, 1.66GHz, 224mb of ram, Windows XP home edition 2002- service pack 2.  I checked the UPS and it says it is currently stopped.

[JJ 3000]

Does your motherboard have onboard video? If so, you may have to go into setup and disable it, and then reinstall your new card and drivers.

[patio]

The computer is an ACPI Uniprocessor pc, plug and play monitor, amd sempron 2400+, 1.66GHz, 224mb of ram, Windows XP home edition 2002- service pack 2.  I checked the UPS and it says it is currently stopped.

Not the UPS...the power supply.
How many watts is it ? ?