At this stage of the game, I only see 3 options.
(1) Obtain (can barrow) a win 7 installation DVD. Use only to see if it can repair you Operating system. It might be able to repair and re-install all the incorrect drivers. On a 25/75 % chance, but worth a try.
(2) Contact Tosihibia for a Recovery DVD. Cheaper, easier, but slower than option 3
(3) Buy a copy of Win 7 and reinstall. Will need to download and install any drivers that you may need.