Vista - Limited acces to C drive

Please help.....After I shared my C drive on a network it was working fine.....I then unshared it but something went wrong and said the hard drive would be in a mixed state if i didnt continue the operation fully....i ignored it(idiot) and carried on....but now i cant access my C drive directly but i can access my documents....i was thinking i would just system restore it but i cant even access that and i cant back up my files either.....but i can access them.....i have tried changing permissions in the security tab of c drive but it wont let me stating that access is denied....and i have tried to enable the guest account but it wont even open up the window to do so.....please help.....i really dont have any idea what to do
Masood