Replying to Paging Dr. NS - computer help

This whole not having a Mac thing is pretty frustrating, cause' i'm thinking this is a virus.  My Dell will start up to the logon screen, lets me put in my password, but then gives me this error, then moves to a black screen:

Windows Logon:  LogonUI.exe - Bad Image
C:\\Windows\system32\slc.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.

So far I put in the Windows7 disk and tried to repair the uh oh, but when I do that it tells me to unplug whatever I have plugged in. There is nothing plugged in.

So, i'm wondering what I should do here.  I'm really trying to avoid losing my files.