If this computer used to boot from the same cd and cd drive fine and no no longer does, and if you have checked your BIOS boot order, then my guess would be that the drives are not jumpered right. While there are multiple ways to configure the system, I would suggest that the hard drive be on the primary controller. If there is only one hard drive it must be jumpered as master (or a few older drives had a jumpering option that had to be selected if ony one drive was used that differed fro the master setting) If you add a second hard drive it gets jumpered as slave and the first one must be master in that case. The CD dtrives should be on the second ide controler. The first one must be jumpered as master, the second one as slave. Never use the CS jumper setting.

You might also want to look into using Smart Boot Manager, but attend to the above first. SBM is not going to correct any jumpering or configuration problems.