I'm not sure you are following the correct steps.Try this walkthrough:
Boot your computer to the Windows 7 DVD
Choose to install now.
Select your language and click next.
Click the button for "Use recovery tools".
Now select "Command Prompt". You may need to run as Administrator.
Type the command: bootsect /nt60 C:
Restart your computer and Windows 7 should boot as the GRUB loader is now eliminated.If not, to get the Windows 7 GUI start-up back, now use , as before the command: bootrec /fixmbr
Now try for another reboot.
You can then remove all traces of the Linux distribution