First of all, hello all, I am quite new to posting here. Previously, I confined myself to the PCI Video Card thread, due to my interest in mini-ITX systems. So here goes: Up until not so long ago my rig consisted of the following: Intel Q6600 P5N32-E SLI 2 x 8800GT in SLI 4 HDDs (2x160, 1x200, 1x320) 4GB of Corsair XMS2 800Mhz DDR2 Antec Truepower Trio 650W Thermalright IFX-14 + 3x120mm fans. Nxzt Tempest Case. The P5N32-E SLI is a rather sucky motherboard for OCin' Quads, and I decided my graphics setup wasn't quite cutting it anymore (In my opinion, I know it might sound a bit nuts), so I went for an upgrade. I ordered the MSI P45 Neo motherboard and the Sapphire HD4870X2 video card. This is where the problems began. I have built the new system, connected the 6-pin power connector from the PSU and the 8-pin power connector via the 2-molex-to-8-pin adapter supplied with the card, re-formatted the system drive and reinstalled my Vista ultimate 64-bit. After installation, the system began to lockup at the desktop. This happened even before any GPU drivers were installed. I installed the latest video card drivers from ATI, but the freezes continued. I removed the drivers and installed the drivers from the DVD that came with the card - the freezes kept coming. I installed Vista SP1, same effect. I replaced my 4GB of memory with two PQI DDR 800Mhz sticks of 1GB each I pulled from another modding project of mine (where they work flawlessly), and it did not help, either. I disconnected some of the fans from my Nxzt Tempest and disconnected all drives but two HDDs, to no avail. Needless to say, my system is currently running at stock clocks. It would still randomly lock up at the desktop. The one time I managed to run Crysis it was sluggish as hell at 1680x1050 on High settings (with no AA or AS) and promptly locked up about a minute into the game. I ramped up the fans to maximum (a 747 is quieter, I assure you), but that did not help, either. I decided the card is the problem and returned it to the store. They tested it, and called me back saying it passed 6 loops of 3dMark06 on their XP SP3 test system with no problems. I came there, asked them to show me it actually works, and they did. It completed 3DMark06 with no issues whatsoever and I took it back home. I installed one of my old 8800GT cards onto the new motherboard. It works flawlessly. So currently, I am stumped. The remaining possible culprits are (I am most likely missing something obvious): 1) I have heard of P45 motherboards not working well with the HD4870X2 in some BIOs versions (But those were Gigabyte boards, so I've no idea whether this is even remotely relevant, but it is a possible cause). 2) My venerable Antec Truepower Trio 650W is unable to power the HD4870X2 in a stable manner (But the rig freezes up even when idling on the Vista desktop). 3) The P45 Neo has some compatibility issues with the HD4870X2 (I am sure someone would've come across this one by now). 4) My motherboard is borked (But then why the 8800GT works flawlessly ?). I surely hope it ain't #4. If I have to remove and reattach an IFX-14 again I am going to kill something. My current best bet is #2 and I have managed to get my hands on a HEC 750W PSU (My friend has one in a server), identical to the one the store used in their testing, where the card worked. Okay, and now I ask, anyone has other ideas as to why this goddamned card won't work ? If anyone has heard of any compatibility problems, or issues about a rig close to my new specs, I'd like to know as well. Thanks.