Currently I can login to windows 7 if I boot from CD rom and ignore the prompt to use the boot disk.
When you try to boot normally what error do you get ?

Boot from the CD

When you reboot you will see this although yours will say windows 7. Click repair my computer

http://i1224.photobucket.com/albums/ee362/Essexboy3/RepairVista_7275.jpg

Select your operating system

http://i1224.photobucket.com/albums/ee362/Essexboy3/RepairVista_7277202.jpg

Select Command prompt

http://i1224.photobucket.com/albums/ee362/Essexboy3/RepairVista_7277.jpg

At the command prompt type the following

Bootrec.exe /FixMbr

[*]Once finished type Exit

Reboot to normal windows and run MBRcheck again please