Yah I had the same prob. Once DetXP started coming out, they became incompatible with NVmax. I'm sure its something to do with the registry, but I've been too lazy to research it. Having already had NVmax installed rendered it useless and gave random error messages, but it also unlocked the same capabilities within the nVidia tools under advanced. But then I started getting nv4disp.dll errors and crap during games, so I had to reinstall Windows. Anyways, I just went with Rivatuner instead of trying to find a hacked version of NVmax that works with DetXP....it does everything NVmax does, albeit a bit more cryptically.
Chiz