Hi
If you Google 'the user profile service service failed the logon. user profile cannot be loaded. windows 7'
it comes up with many suggestions
these are complex repairs
If you do not feel confident get some one with the necesary skills to do it for you
It helps if you have alternative accounts on the PC
Possible Causes
Have you had a shut down because of a flat battery (without auto shutdown working) ?
or pressed off button as you thought system had crashed?
best of luck
Mike Barnes