Updating the BIOS may be helpful, but I suspect you have a hardware problem. Friday and Saturday, I moved a triple-boot (Vista 64-bit, XP Home, XP Pro) from a 6150 such as yours to a Vostro 220s and I was able to reconfigure all three to work properly; the biggest issue was waiting for the hundreds of Windows updates to download and install. The Catalyst Control Center refused to start on the XP Home install, until I uninstalled and reinstalled all the dot-NET runtimes, uninstalled all the ATI assemblies from the GAC, deleted the ATI folders, and then reinstalled Catalyst.
You might try swapping in a known good working power supply, and inspecting the motherboard for bulging capacitors.