Windows Server 2003: Drive Letter Dissappeared

Tshooting a Win-Server 2003 server with built in Motherboard SATA RAID feature controller, 4 SATA drives on four separate SATA motherboard connectors. The C:(RAID)volume lists ok everywhere, the Data (RAID) volume appears in BIOS and Diskpart sees it but not listed in My Computer or Disk management. Can't access it as a network address. This volume was "E:(Data)", but I think it should've been D: because the DVD drive is currently E: and D: skipped and not listed. I did the Diskpart assign command (volume=D) in Diskpart, but no fix. Both Data drives read/write tested ok in other setup. C: RAID volume works, so I suspect SATA drivers are intact, and no errors in dev-mgr. The sys was working fine for 2 years. Just started missing Drive letter assignment to the Data Volume? Any clues? How would I reinstall SATA drivers? Would a RAID repair delete the data? I have disabled and re-enabled the SATA & Disk(listed as Data)drivers in Dev-Mgr and BIOS SATA RAID features and still doesn't re-assign a drive letter to the RAID volume. Anybody?