Use Partition Wizard Bootable CD to delete and create your partition, choose primary partition during setup. Also set partition active using the modify option in Partiton Wizard. Take out the PW cd, drop in your Windows 7 dvd and reinstall.
How to create PW Bootable cd. Download the iso and burn to cd using ImgBurn the 2 links are here.
Partition Wizard Bootable CD allows user to manage partition directly with partition manager bootable CD.
The Official ImgBurn Website
Only delete the partition you want to install windows on.