windows server in place upgrade hangs

Hello,

I attempted an upgrade on a physical server from Windows server 2003 x64 standard SP2 to windows server 2008 r2 enterprise and it hangs at the last stage “transferring files, settings and programs” on 40%. It lasted about 2 hours then I rolled it back to 2003. Anti-virus software has been removed. This was done within windows not booting directly to setup.

Any ideas??