It's a wild guess but please have a try at this: (also please be advised my translation from Dutch towards english could be a problem)
Goto start en RIGHTclick on the My Computer icon, revealing a window with some choices. There should be an option like "manage"or something (beheren in Dutch) Leftclick that option what should give you a window like ton the screenshot.
Find the map: local users and groups (or something alike), open that and find the map users. In that map you will find all the users who have acces on your computer. Rightclick the username in the right window and choose "properties" (on the screenshot i used the administrator as an exaple, you of course should click the user missing)
Then be sure the option: account is...