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To add to Johannes Rudolph's answer...The Jon Alb article is the best for a simple breakdown on exposing Team City in IIS 7.5. The only thing to mention is that if you are running other sites on that server instance, after you follow through his second part, you might need to create a dummy site looking for a subdomain host header value because it seemed like IIS never executed my farm re-write url if there was no site that matched. However, this should also allow you employ HTTP Authentication if you want to protect your Team City login page on port 80.