Let me be more clear ... you CANNOT repair the OS with SBUU.  The only thing that SBUU will do is help you re-install Windows, and it will WIPE OUT all information on your current disks! You said Server 2003 will not boot - it just keeps rebooting at the Windows screen.  If you want to fix this, you must boot to the 2003 CD to Recovery Console.  Since 2003 cannot communicate with the drives without a RAID driver, you will need to load the RAID driver (below) from a floppy disk at F6 during Windows Setup (the very first thing you see when booting to the Windows CD).  Since your T300 probably doesn't have a floppy drive, you will need to use nLiteOS.com to integrate that driver (text-mode) into the 2003 media. If  you don't care about the data on the disks and want to wipe everything out and re-install Windows, then use SBUU, but that doesn't sound like what you are trying to do. RAID drivers: Use this if you have a PERC 6/i:   Use this one if you have a SAS 6/iR:  
Hi, My PE T300 With Windows Server 2003 keep restarting when loading Windows,i need to repair the O/S but i lost the boot CD for my PE T300.im begging you to give me the link (iso link if capable) where i can download it.   Thank You So much!
DELL PowerEdge T300 boot CD