well the profile must have been password protected which u r trying to access... wat all u have to do to get around this problem is .. just Right click on that folder choose properties click on security tab choose advanced... click on ownership.. choose your username and check the "replace owner on all sub folders...".. and then... click ok and get back to the security tab .. now choose ur username and assign it all the permissions and u'll b able to access the folders....
note: if u cant see the security tab go to folder options menu in control menu and in the view tab uncheck the "use simple file sharing"
Arihant
^^ better option is to add the vista login name as a user with full permissions.
if the default permissions are replaced by vista, then xp wont get access to the folder. if he is using xp then he will get all sorts of problems when using that os.