Six weeks ago I bought a PowerColor HD 4850 PCS. I get endless freezes, crashes, restarts and BSODs in 3D games. Initially it was running on XP pro. More recently it is running on a fresh install of Vista. Same problems so I am assuming it is not a driver issue. I RMAd the card but the online store tested it, found it was OK and returned it - charging me £21 for the privilege! Temperatures seem OK – no higher than 70 degrees or so. My 2GB of Ballistix memory passed Memcheck, although I only had time for one run. I then started to look at the PSU. I have an old Antech 500 watt. I then tried two different PSUs, one 550 watt and the other a Jeantech Arctic 600 watt. Neither cured the problems (but admittedly they were not great PSUs). However, I hit upon a bizarre set up that does seem to cure the problems. The original 500 watt PSU is installed as normal, with a molex connection direct into the Asus A8N SLI Deluxe motherboard near the PCIe slot. However, the dedicated PCIe cable is NOT used. Instead, if you plug the Jeantech unit’s PCIe cable into the graphics card the problems seem to go away EVEN THOUGH THE JEANTECH UNIT IS NOT PLUGGED INTO THE MAINS. The 4850 must be getting all its power from the PCIe slot direct. If the dedicated PCIe cable is plugged into the card but not into the (disconnected) Jeantech PSU, the PC does not boot and instead asks for a cable to plugged into the graphics card. If the cable is then plugged into the Jeantech unit then, even though this is not plugged into the mains, the PC boots and the graphics problems do not seem to be present. I cannot run the machine with a brand new disconnected PSU sitting next to it so need to find out what all this means. I am thinking of swapping my single 4850 card to the second PCIe slot, although I am not sure if my motherboard will allow this.