Diamond X1950 Pro installation

I have searched for this answer, but couldn't find it. Do I have to plug a power cable into both connections on the card? I'm running an Antec True 480. The specs on the PSU show 22amps on one 12 volt rail. I have only one power cable plugged in (the one directly across from the DVI connection I'm using). All goes well until I try to play any game, view a video clip or slideshow. When I do any of these, I hear the video card fan go into high gear, then the weird artifacts appear, and the monitor goes to sleep. Also at boot up I get very weird artifacts until the actual BIOS screen appears.

I'm running two optical drives, onboard audio, one 300gb PATA hard drive, an Intel P4 3.0 ghz cpu, and a ton of fans and USB connections. OS is Windows Vista Home Premium, and forgot to mention that this is an AGP version of the x1950 Crossfire. I plugged another connector into the card and still get the same results accept this time the computer rebooted itself. Vista Problem reports and solutions app says it was the ATI drivers. I'm running ATI Catalyst 7.4 after trying the 7.10. I'm trying everything I can think of before I drop bucks for a new PSU. Anymore advice?

Ok, I got it working last night. I actually have two hdd's installed and I unplugged one and ran a power cord splitter for extension. I played MOH Airborne and COD 4 SP demo. Today I plugged the second hdd back in and she ran fine for a while. Then I lost the second hdd in My Computer and started having problems booting. I unplugged the second hdd and she's back up.....must be the PSU in conjunction with the additonal hdd. Your thoughts? One more question..the box actually says that I need a 550 watt PSU with 38amps on the 12volt rail.

Yep, that was the same response I got from the techie at a mom and pop computer retail store. The label goes on to state that an 1100W PSU is reuired if two cards are used in CrossFire mode. Thanks for the PSU recommendation. I think I'm going to get the Antec....seems to be the best bang for the buck. My card specifically is the Diamond Dual Link DVI Crossfire X1950 Pro with 512MB DDR3. I played the Crysis demo last night and it ran superbly. My only real bottleneck now is the P4 processor. I'm saving up for a new rig.