Hi, My Mac Documents folder has a folder called, "Parallels", and in that folder is a folder called, "PC Backup". This folder is filled with files named, "Mac WinXPxx.sos" where xx is a sequence number. They take up quite a bit of room (the smallest is 1.75 GB, the largest is 15.75 GB); so I am interested in removing some of them if it won't mess things up. I can't find anything in the User Guide that pertains to .sos files. A search for snapshot files reveals extension like, .sav, .mem. I am using Parallels Desktop 6, running Windows XP. The .sos extension may refer to something like, shared OS - ??? Anyone see these files before? Bob