CD_ROM not working, help please

My CD/DVD drive disappeared from My Computer and Device Manager. So far I have tried:
1)checked BIOS, no CD/DVD drive on Boot Sequence and Drive configuration
2)replaced with new IDE cable and CD/DVD drive
3) on Regedit, deleted Upper and Lower filter
4)download Dell diagnostic utility, during test run, cann't found CD-ROM in the menu.
5) updated BIOS

So far, still can't find CD drive. My computer is Dell Dimension 3000.

Any suggestion? I am desperated.

Dreamdream