Hi,
read the following document (Windows XP section):
http://www.apache.inetcosmos.org/dist/httpd/binaries/win32/README.html
Ok, they write that accessing the server with localhost or 127.0.0.1 "generally" doesn't lead to that error.
Depending on the configuration of your IE it will redirect to the MSN search page instead of displaying the famous 'Cannot find server or DNS Error' page.
Looks like you're having the problem described in the document above.
Seems like there is no other choice than installing SP1 🙁