You don't need to necessarily delete the backups - backups being stored on the file system will not cause a problem, but you could prevent them all from being opened when the program starts, which is what I think you mean. If the program has an error when opening, it could be caused by a document opening that has an error on load, so preventing the backup from re-opening could solve the problem.

Certainly deleting random files in the AppData folder is bad advise and should not be followed. The default location for backup files created by Xara programs (WD, PGD, DP) is within the AppData folder, but again I'd not recommend deleting these on a whim. Only delete files that you know what they are for and why you are deleting them, regardless of where they are stored.