Work through these steps for
Troubleshooting Windows 7 Failure to Start
starting with the hardware tests in the introduction since they are indicated.
The steps sequence the order which repairs need to be run, since hardware must be confirmed first, then check for infection since the OS may not repair until disinfected, if then.
Once cleared of infection, the most important thing is to confirm WIn7 or System Reserved (preferred) is
Partition Marked Active to run
Startup Repair - Run up to 3 Separate Times since it won't repair if the correct partition is not Active.
Since you can mark Active using
Partition Wizard CD, if you want to skip to those steps using it's CD and include
Partition Wizard Rebuild MBR, before doing so post back a camera snap of the maximized PW drive map and listings so we can spot potential problems much more easily for you.
Everything that can possibly be done to start Win7 is compiled in the tutorial, leading up to if necessary rescuiing your files to get a perfect
Clean Reinstall . An in-place Upgrade from Vista is often not a good install, so you may also want to skip to that step.