I recently discovered that in the Parallels folder which is in the DOCUMENTS folders I still have stuff from previous installations. That was there since 2008. In fact with the actual version 7, the only think that is needed is Microsoft Windows XP.pvm. Inside this package is all you need. I was able to remove like 100 GB by deleting the useless stuff and removing some snapshots that were too old to be useful. I think that it could be indicated in the Read Me that this can be deleted.
Data is in the PARALLELS folder in the DOCUMENTS folder this is not a temp data. The data was used by previous installation of Parallels. it is located in the Parallels folder which is in the Documents folder like other type of data. Are you a Mac user ?
For those wanting to delete the data be careful. What remains in my Document Folder is only Microsoft Windows XP.pvm. All the previous data have been removed. A good way to test would be simply to move the useless data out of the folder and start Parallels. If you deleted the wrong stuff it will not work.
