Hi guys trying to get up and running again here.I have an ASUS A8N32-SLI Premium board with an ALTLON64 4000+, 2GB OCZ plat. RAM. a 7800GT 256MB card with an ultra 600 Watt P.S..Today I bought a PNY 9800GT 1GB PCIE card.my port is PCIEx16 and the board and card MFR.s said the card would clock down to x16 specs.Inital boot was flawless and managed an MD-11 departure from ORD to DFW with a turnback to ORD (new dest. entered in FMC ILS flown to rwy 28)I had a black screen CTD short final ORD. I then flew meigs to ORD rwy 28 using map to put me airborne over meigs,The visual quality was stunning, no stutters or blurries. after exiting FS I did a few things in windows explorer and things slowed down greatly. it almost seemed as if the Hard drives were running slow. after that I got a BSOD and the computer would not reboot. (nothing when power switch pressed.) I thought the P.S. had quit but it works after you pull out the power cord and replug it in.With the 9800GT installed, after every shutdown you must remove and reinstall the power cord or the computer will not boot.I reinstalled the 7800GT and all went back to normal.Does the 9800GT draw enough power to cause this or is something else amiss?does this sound like power issues as they are random and non descript?I must note that I also run 2 120MM, 1 80MM fans and 2 hard drive cooler fans as well on this 600W power supply.To make this run right how much power woud I need?Stan

Really sounds like a bad from stock card. That'd be your 1st step. 600 watts is plenty for and AMD + a 9800GT.

Thank you Sam, I'm heading off to exchange the card now.I used ASUS PCPROBE to look at my voltages last night and found the 12V rail showing 11.90V with an intermittant fluctuation to 11.84V. Is this a normal range or a sign of a dying PS? off of this 600watt PS I'm running the board and CPU, the 9800GT, 2 sata hard drives, a DVD burner, 2 120MM and 1 80MM fans and 2 twin fan (small) hard disk coolers.Am I asking too much from this thing?Stan

That's a normal 12 volt flux. Check Vs under a load once you get it running. You'll see +/- .05v differences with the various measurement tools. What brand of PS? That makes all the difference. However from a name brand 600watt'r, that load is no problem at all.