The PERC 320/DC is a rebranded Adaptec controller, so while Adaptec may not have a 2003x64 driver, Dell does.  There are not 2003R2-specific drivers.  You can try (if you haven't already) one of these drivers: 2003x64: [URL] XPx64: [URL] There is a good chance that you will need SP2 installed in order to install it. I would try a non-RAID SCSI controller, like the 39320:[URL] 2003x64: [URL]
I just bought this Dell sc1420 tower server.  I bought a SCSI tape backup unit for it.  I also bought a Dell N5694 SCSI controller with cable.  My problem is that I have used every version of the driver files that I can find.  None of them will install.  I have Windows Server 2003 x64 R2.  I have 4.0.0.5813 firmware version.  Is there a valid driver file lurking somewhere on the Internet?  Or do I need a better, more updatable SCSI card?
New a driver