If you are logged on with administrator privileges you should be able to access the contents of any files on the system. You dont give any details of why you installed (The problem could be related to the reason for the re-install) or whether you gave the user the same name as the old user (Having two users of the same name may have confused the system). If logging on as a user with administrative privaleges cant solve it I dont know what else to check, you may have to pay a specialist data recovery service to get your files back.