LOL, I'd love to know what you did in C that erased the MBR.
Anyway, if you're running Windows 9x/ME, just boot the computer using the startup disk/install CD and in command prompt just type :
fdisk /mbr
That will recreate the MBR for you and you will be able to boot back into Windows.
If you're using Windows 2000/XP, boot using the Install CD, press R to enter the Recovery Console and type:
fixmbr
and follow the instructions.