If you only want to have Windows 7 on your hard disk. Then all you need to do is boot the computer from the Windows 7 DVD.
Start it's installation, and during installation use the Windows 7 disk manager to delete the Ubuntu partitions and have it create a new Windows partition for you. The Ubuntu partitions are probably listed as unknown, because Windows can't access ext4 fomatted partitions. After that just continue installing Windows 7 and you're set.
Last edited by SandsOfArrakis; 08-14-2013 at 09:09 AM.