As the computer is booting into Windows, turn it off with the power on/off button.
When the computer is turned on the next time, Windows should notice that the computer did not successfully boot and give you the Options Screen.
From the Options Screen, can you get into Safe Mode?
If not, try the following:
Download/install SuperAntiSpyware Free Edition:
It has an option to restore the SafeBoot key that is deleted or corrupted by malware.
Download the program
Save to the Desktop
Double-click on the SUPERAntiSpyware setup file to launch the installer.
When done installing, open SuperAntiSpyware
Click on Preferences
Click: Repairs tab
Scroll down and select Repair broken SafeBoot key
Click Perform Repair and follow the prompts.
When done, start SuperAntiSpyware again, select:
Scan your computer > Perform a Complete Scan
Once again, on the main screen, click on the Preferences button.
Click on the Statistics/Logs tab
Double-click on the most current log.
Please provide the SuperAntiSpyware log in your reply.