The command is as follows. For DOS users, restoring your MBR and getting rid of LILO is just one simple command. Re-installing Windows is one of the most common reasons for this. Just about every Linux distribution these days is available on bootable CD's. We've had terrible times searching for a working clean floppy for a boot disk and we don't recommend boot disks.
Most distributions provide such images.
Download one, follow the instructions and you'll soon have a working boot disk. If you're booting off the CD then you might have to do some work after you boot. Red Hat has a rescue mode that you select after booting. You can use this shell prompt to continue with the recovery. Boot in and enter the following at the prompt.