What operating system did you upgrade to? Exchange 2003 is an email server not an operating system.
Did you upgrade to Windows 2003 Server, Windows XP Professional, Windows Vista?
If you are using Windows 2003 Server HP does not provide drivers for your scanner for Windows 2003 Server. Usually the Windows XP drivers will work on Windows 2003 however.
This page on the HP Support site shows all the available drivers.