This appears to be related to an AHCI/IDE driver update which renders the PC unbootable.
Here is a solution that works on Toshiba Satellite laptops:
1) Power on the laptop
2) Press F12 key to enter the BIOS
3) Go to "Advanced" menu
4) Go down to "System Config"
5) Change SATA Controller from "AHCI" to "Compatibility"
6) Press F10 to save and exit

Your laptop should now boot into Windows 7 and you should run windows update and make sure all of your drivers are up to date.