Just bought a used 4870 for my 2nd rig for the express purpose of crunching MW. It works fine on Collatz, but fails all MW wu immediately. With updated drivers it would make it to 80% complete, then get a computational error. With the original disk drivers it fails at 1 second. I'm a Nvidia guy, so any help from the ati folks would be helpful. BTW, it is not OCed. Ask if you need more info, I'm sure I didn't give you everything you need for a diagnosis.
Al

xp 32 - Intel Quad q6600