So you're saying you've deleted the MBR...
Great going. *smirk* (It's okay, I've done it before too when I tried to Hackintosh)
Anyways, you'll want to use the Windows 7 disk to start up, and select the "Repair" option in the bottom left corner of the first window that pops up. Running the Automatic Repair or Startup Repair, or whatever it's called should clear it up.
Should the Startup or Automatic Repair option not work, use the inbuilt Command Prompt and try:
bootrec /fixboot
bootrec /fixmbr
bootrec /rebuildbcd
Hopefully, that should clear things up.