If it does not show up in BIOS then windows will not recognize it. Check if for some reason the controller that the drives are on is disabled. If that is not the case then check all the connections to the drives.
The same thing happened to me after I cloned my C Drive. Both DVD drives could not be seen in File Manager. On the control panel, there were yellow exclaimation marks on both drives. Here is what I did to solve this.
STEP 1 - Reassign all hard drives and removable drives' letters, keeping drive D and E letters free.
Right click on My Computer and go into Manage
Reassign all drive letters in here and exclude drive letters D and E keeping them free as you want to have the DVD drives (assuming you have 2 of them) as D and E drives.
STEP 2 - Dive into REGEDIT in Windows XP
1. Click Start, and then click Run.
2. In the Open box, type regedit, and then click OK.
3. In the navigation pane, locate and then click the following registry subkey:
4. In the right pane, click UpperFilters.
Note You may also see an UpperFilters.bak registry entry. You do not have to remove that entry. Click UpperFilters only. If you do not see the UpperFilters registry entry, you still might have to remove the LowerFilters registry entry. To do this, go to step 7.
5. On the Edit menu, click Delete.
6. When you are prompted to confirm the deletion, click Yes.
7. In the right pane, click LowerFilters.
Note If you do not see the LowerFilters registry entry, unfortunately this content cannot help you any further. Go to the "Next Steps" section for information about how you can find more solutions or more help on the Microsoft Web site.
8. On the Edit menu, click Delete.
9. When you are prompted to confirm the deletion, click Yes.
10. Exit Registry Editor.
STEP 3 - Restart Windows XP
And that should solve your problem!!