You wouldn't be able to delete the SAM file while you're still using that installation. The normal procedure is to use either a Linux bootable CD, another application such as Winternals ERD Commander, or to use a bootdisk as outlined at
http://home.eunet.no/~pnordahl/ntpasswd/
In all these cases, however, you're not actually accessing the Windows installation that you're trying to hack ...er, fix.