I was installing BizTalk on Win XP sp2 machine when I got this message. I didn't understand what it meant. Then I found the solution on the net. Here is the procedure:
1. Start -> Run -> gpedit.msc
2. Click Computer Configuration
3. Click Administrative Templates
4. Click System
5. Click Remote Procedure Calls
6. Click on RPC Endpoint Mapper Client Authentication
7. A new window opens. Enable this service.
That's it!
Also make sure that your firewall and antivirus are TURNED OFF BEFORE you start configuring BizTalk (ConfigureFramework.exe).