Are you trying to connect to SQL 2000 or SQL 2005

Did you try:

From SQL Server Mana Studio, when you click to connect-> click Options and Network Protocols-> Named Pipes.. Check if this works.

else.. Start-> RUN-> cliconfg then disable all Protocols in the right side of the SQL Server Client Network Utility window. then APPLY.

Again First Enable Named Pipes then TCP/IP.. Goto Alias TAB click on ADD, under named Pipes check Just add the SERVERNAME you are trying to conenct and click ok to com out of the window.

Try to connect through SSMS.