1. Delete your current Virtual Machine ( http://kb.parallels.com/5029 ) based on Boot Camp partition.
2. Open Finder, go to Applications folder -> Utilities. Launch Disk Utility.
3. In Disk Utility click on your Mac Hard Disk and then press Repair Disk button.
4. Now start Parallels Desktop and create a new Virtual Machine based on your existing Boot Camp partition ( http://kb.parallels.com/112941 )