First - check with DELL for any driver or proset later than the 2004 version. (We're 2009 already!)
If DELL didn't have newer versions, check out this site: http://www.intel.com/support/network/sb/CS-006120.htm
for Windows 2003 R2, my best bet would be PROXP.exe (Ver:14.3 Date:7/27/2009).
hope this helps!
For anyone upgrading from an early version of Intel® PROSet to a more recent version for your Ethernet connection, you might think that PROSet has disappeared. The early versions of Intel® PROSet ran as an application. More recent versions are integrated into Windows device manager and show up as tabs when you view your device properties.
Reference: Where is Intel® PROSet and what is it?