If you had bootcamp installed, and Parallels Workstation running Windows within Bootcamp; Then you had Parallels Desktop installed on the Mac OSX partition; could you use the same.hdd file for parallels desktop as parallels workstation? i.e. storing the .hdd file on a shared drive or using MacDrive to allow both OS's to see it. Meaning, you could access your parallels files from whichever OS you decided to boot into. Although it would be expensive having to buy 2 copies of parallels.
Well, I suppose this can be done. Some other folks here have stated that the Mac and Windows versions of Parallels use the same disk image format so a VM created by, say, the Windows version can be used with the Mac version.