How do I remove dual boot with Win7?

I explained in my first post that when you don't boot the Win7 installer but instead run it from another OS it will lock out C so it isn't available without a booted reinstall. This is why installs should always be done from booted installer.

As long as D is labeled System Active Boot you are good to delete C. But I would confirm those listings since you're still getting the Dual Boot menu which should have vanished along with Vista boot, unless the repairs reconfigured a Dual Boot which is rare. In that case the Dual Boot should disappear when Vista is deleted - if not install EasyBCD 2.02 to Delete Vista from Edit OS menu tab.

I did just as you said and it works perfectly now.

Thanks a lot for your help. It's really appreciated. Happy New Year

Glad to help.