This is very strange that I have never encountered. The OS is Windows XP Professional Service Pack 2, and the laptop is half-year old. There was only one account, Administrator, when the welcome screen opened and requested to login. After logged in, from the Documents and Settings folder, I saw a lot accounts were created with many personal files on each desktop folder. I went to control panel to create a personal account with admin's privileges and activated guest account. I then clicked switch user to try login to new created account. After login and open some applications, such as word, explore and IE, I then clicked restart the computer, a warning message said there are other users are still login, I then clicked log off instead restart. DISASTER THEN BEGIN ... The welcome screen only shown 2 accounts, personal and guest. The administrator's account was gone. I clicked restart computer, the same warning popped up, but I have no way to logged in the administrator's account to log off the user. I then just clicked restart the computer. The welcome screen shown the same 2 accounts. I logged in that new ceated personal account, and open explore to check if those accounts were still there. I found all the folders were there until "desktop" and all the files and folders in that desktop were all gone! I went to control panel to check how many users exist, it shown only 2: the new created one and the guest. Can anyone help or explain? Thanks!