Regarding the error "VDS fails to claim a disk" which occurs in Windows Server 2003 when switching from one SCSI controller to another, Microsoft has a hotfix, but you must call Microsoft technical support to get it.
Windows needs to know that a controller is being removed through Device Manager before physically removing the hardware.
This bug causes Disk Management to not load properly. While I was able to start Windows, some logical drives were missing, and I could not make an ASR disk to run the Windows repair routine. In trying to fix the problem through Windows, I made matters worse, and Windows would no longer come up at all.
I managed to fix the problem by ghosting the OS partition to an IDE drive, deleting the SCSI device drivers and hardware, then booting to Windows on the IDE drive. At that point I reinstalled both SCSI cards, but no SCSI drives, that were previously in the computer. I removed both SCSI controllers in the Hardware Manager snap in, then reboot with just the SCSI card that I wanted in the computer and installed the driver for it. Last step, ghosting the now working IDE partition back to the SCSI drive, removing the IDE drive, brought Windows and Disk manager back to good health on the SCSI controller and drives.
Occurs in some Windows 2003 Enterprise Server setups when setting the "Restrict CD Rom to locally logged on users" policy in security setting. No real reason as to why yet. Other systems work fine with this configuration. Temporary fix, set the policy to "Disable" and leave cd rom access open to everyone.