You didn't mention what windows version you have or I would have explained in detail how to create a bootdisk and how to use it. You can obtain a bootdisk for almost every os from here
http://www.drd.dyndns.org/fr_index.html?/disks.htmlCreate the bootfloppy and boot from it. If the system won't boot from floppy. Check the boot sequence (order) in the bios and make sure it is set to boot from floppy 1st. To restore the mbr >
Windows 95/98/me: boot from the floppy and at the prompt type: fdisk/mbr
Windows XP: boot from the xp cd, enter the recovery console (F2) and type: fixmbr
About the problem with your cdrom, it would really be helpfull if you tell us more, like:
1) What windows version
2) Did it work before
3) Does the bios still recognizes the cdrom
4) Is there an error in device manager
5) what did you do just before it disapeared
6) are the cable still attached properly
7) do you experience any other problems
etc etc.