I installed Office 2000 and UR on Win 2K SP4, configured .doc for displaying in browser view, and an imported .doc file is shown internally in UR. Explorer also has the Advanced options in file types, with Browse in same window checked.
It sounds like something is flaky with your W2K and/or Office installation. Some possibilities:
http://www.google.com/search?source=...e+windows+2000