if it is not...
you dont need to format. but i suggest it.... (that way u dont get more problems later...) but u might not u never know
here is how to fix it....
Lets say your cd drive is called L ok? put in your windows cd and hit X when it comes up.. then:
go to your command prompt
-> type in cmd
ok from here type this in: (make sure ur EXACT)
expand L:\i386\autoexec.nt_ c:\windows\system32\autoexec.nt
IF that doens't work, you have 2 more options before formatting
one is u post back and we'll try another thing to type in... if not try this link: