I'm guessing that you want to reinstate the default win7 bootloader in place of grub (the bootloader ubuntu installs) so that you can then recover the disk space from the ext partition.
I'd go to
http://ubuntuforums.org/ and search around (or post a question) or go to microsoft.com and search on "remove grub" or "remove ubuntu". A quick search on MS gave me this link.
http://social.answers.microsoft.com/...d-4cbadd7c933c
You may also have to look up how to create recovery media.