I was running Desktop for Mac 3.x. Installed 3.0 build 5608, but when I started an XP VM, the process hung in a CPU-intensive loop. Tried to re-run Desktop and got "can't run" with "-600". Uninstalled, fixed disk, etc., and reinstalled. Same thing. Tried to install a year-old .dmg I had saved (build 4124), but that fails, too. My virtual disks are intact, so no data lost, but I can't seem to run any version of Parallels Desktop, old or new. I'd be happy with a good install of 2.x, but I don't have a recent installation .dmg, and even then I'm not convinced I could get it working. I seem to have messed up something somewhere.