Can't you just go... (I'm using 2003 with Business Contact Manager)
1) File menu, Import and Export, Outlook
2) Import from another program or file (next).
3) Tab Separated Values (Windows)
4) Navigate to the file
5) Select destination folder - choose Contacts
6) and so on.

Note: In my mind it would be easier to use Excel than a tab delimited file. I would migrate the txt file into Excel first. It's easier mapping.

Also, if you get errors then create an Excel template file from Outlook by using the "Export" function (similar to the "Import" function above).

Good luck.

Andrew

PS. Another place that may be useful to you for Outlook questions is http://www.outlook-tips.net/archives/2004/20041018.htm.