I asked the same question about a month ago (and unfortunately didn't receive a response), but thinking further about it surely you could use a 'disk image' package like DriveImage or Ghost to create a backu0p copy of your virtual Windows installation. Then just restore this disk image over your Bootcamp installation.
There is the issue of Parallels tools being different for virtual vs. Bootcamp, but presumably you could boot into safe mode on your Bootcamp partition and remove/reinstall Parallels Tools.
Has anyone tried this, or do you have any views on whether it would work?
Thanks,
Tom