Backtrack 5

I am fairly new to Linux and have been experimenting with Backtrack 5 for penetration testing. I have used it on 3 computers and this is the first time that it has caused a problem. I recently used Backtrack 5 (installed on a flash drive) to boot the PC which runs only Windows 7. I messed around on Backtrack a bit after starting it up but did not change any settings, as I simply did not know how. I looked at directories and changed directories and that is pretty much it. I shut own the computer and removed the flash drive. Now when I boot up Windows I am able to access the users and task manager via CTRL ALT DEL but when I click on a user I receive the following message before being sent to a black screen which should be the desktop:

C:\Windows\System32\dhcpcsvc.DLL is either not designed to run on Windows or it contains an error. Try installing the program again using the original installation media or contact your system administrator or the software vendor for support.

I have rebooted Windows into Safe mode with networking and can access the internet despite the fact that is says no networks are available (I think this is due to the fact that most Windows functions / applications are currently unavailable for use)... Any ideas? Thank you in advance!