Attempting to use PC Restore but do not have admin name or password

Hi there. 

I am helping my father with his Dell desktop computer.  Windows is getting stuck during the start up so I have been trying to use PC restore to restore his computer.  The process asks for an administrator name and password but my father cannot remember his username or his password.  :emotion-45: We are not able to proceed to restore his computer without this information.  What should we do?  (We do have a Windows reinstall DVD that came with the computer and we tried to use that but the computer is not reading the CD.  So, we are attempting a PC Restore using just his computer.) 

Any help would be greatly appreciated!