OT question about XP and SuSE backup

Hi I have succesfull backup server with SuSE 9.0 in my LAN-system, where we have Linux, Win-98 and XP workstations. The thing that bothers me, is that XP keeps creating a strange file in the D:-drive. The file-name is tilde (~). I have means of deleting this file, so it does not create any more problems with Linux. But does anyone know why XP keeps creating this file, and it does have all the e--mail addresses from Outlook express. User has succesfully deleted the messenger, so that is not the source of this.. Sorry to ask OT question here, but I have not found any answers anywhere. Jaska.