user profile service failed to logon

my frnd is having dell inspiron n5050. he is not able to login to windows 7 because he is getting an error msg : user profile service failed the logon. user profile cannot be loaded. he didnt changed the password, still not able to login . he has installed 2 windows xp and 7 , and is able to login to xp but not on win 7.
how this problem can be solved ?? ..
thanks in advance