[Blind-sysadmins] Dell PE 840 woes

Hi all, I need to do a reinstall/rebuild ofa Dell PE 840 with Win 2k8. After the first build DVD it asks me for a second update DVD. I found the image on Dell's site but it needs a service tag to download it. The pair of eyes I borrowed couldn't find a service tag anywhere on the outside of the server. Does anyone know where the service tag may be or is there anyway to obtain it from the BIOS? Really appreciated Frank