That you can access the drive at all is good. Your personal files should be in C:\documents and settings\username. There should be multiple folders in documents and settings, one for each user plus and administrator and an all users folder. Try opening the folder for your old username. If it shows as empty with a mouse hover and gives a permission message when trying to open it, then you need to take ownership of that folder and it's subfolders. There's an MS kb article on how to do that.
http://support.microsoft.com/kb/308421