Lost CDs after software upgrade

After loading a update to our CD burning software(Nero). Upon rebooting the WIN2K system could no longer see any CD drives.
SYSTEM:
Dell 700
WIN2k Pro
256 RAM
All devices were working before upgrade.

Symptoms:
IDE Reader shows “!” (Possiable corupted Reg) Does not show in drive listings or Drive mamanger.
SCSI Burner shows all OK. Does not show in drive listings or Drive mamanger.

Actions:
Remove software. No help.
R&R both CDs No help.
R&R Both Controllers. No help.
Run repair from W2K CD. No help.
Remove SCSI ref. in Registry. No help.

Any Thoughts