Same here - lost hard disk
Pretty much the same thing happened to me. Imac core2 duo 2.4GHz. I had parallels 4 working great and it is faster than 3. I was playing with the configure settings. The 2 CPU option is great. Then I changed the memory to 1024MB and the next time I tried to start the VM, it cant find the hard disk (boot camp). I tried all of the above work arounds but it just got worse. So I completely uninstalled with the uninstall program and checked to remove everything the uninstaller had to offer. I then deleted the parallels folder under Documents. Reboot. Reinstall parallels 4. Now its starting to work. Oh wait, windows now thinks there is all new hardware. Restart windows. Install parallels tools. Restart windows. Windows still thinks some hardware is not installed. Let windows install drivers (parallels tool and video driver). Winblows needs to restart again. UhOh, now winblows needs reactivation. Activate but have to call. REstart winblows. Hea, it works. I'm back to where I was yesterday. Guess I wont mess with any more settings for now. Frustrating but it is better than 3 when its working.