Server 2003 hangs on boot in normal and safe mode

I have a Windows Server 2003 standard edition with sp2. In a workgroup and runs web pages. It is running on a HP Proliant DL380 G5 server. It has been in operation for approximately 6 months. Two days ago during a reboot the server started to hang in normal and safe mode. I tried a repair and again it hangs. HP diagnostics has not found and hardware problems. Any ideas.