Vista Tutorial - windows corrupted file

hi turned on my pc and got this-windows could not start because the file is
missing or corrupt -\windows\system\32config\system\
it then goes on to sayi can repair the file by installing the original set
up cd, however i no longer seem to have this-can i buy another one?
i found some info on repairing files which said to hold down f8 with a menu
of options-boot in safe mode,safe mode with command prompt,start windows
normally ect i tried some of these but still with no luck and thats where i
gave up and decided to ask for help!! Is this the end for my poor pc or can
this be fixed, if not by mysel fby someone more experienced?
(sorry if this is the wrong group but there were so many to choose from and
this sounded right)
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lachygirl