Hi
I had a call the other day, where Windows refused to load because MSVCRT.dll got corrupt, what you could do is replace it with the MSVCRT.dll from your windows CD and rename the current one to MSVCRT Old (For backup purposes)
If you want to replace the DLL you can do it in windows or boot into DOS and use the copy DOS command to overwrite the bad MSVCRT
My call I worked on was for XP, but im sure it will probably work for you also
Thanks
Jamie