cd/dvd drive not found

when i boot up my computer i get the message saying cd/dvd drive was not found, consult the troubleshooting section of your user manual. i am running on xp and the drives dont show up in either my computer or device manager. i have deleted the upperfilter and there was no lowerfilter. that worked for a little while but then the drives disappeared again and the upperfilter also never returned. i have also tried to restore the registry to an earlier time and that worked for a short time but then the drives were gone again. i have also gone into bios and loaded the optimal defaults which didnt work. i have changed the ide cables, changed the battery, and swapped the drives. the thing that seems to work is when i run chkdsk, but the drive will be there for a little while and then disappear again. i am not sure what else to do please help!