Symptom: When you install PerformanceGuard, specifically the PerformanceGuard web interface, you get a message that says that port 80 is already in use.

Possible Causes & Solutions

Port 80 is used by another service.

However, it can sometimes be difficult to see exactly which service it is that uses port 80:

In some cases you may see that port 80 is used by a system service with the PID 4 (short for Process ID 4). That system service is typically a listening service from either Skype or SQL Server Reporting Services.
In other cases Windows will say that it could not obtain ownership information. When that's the case, it is typically the http.sys service that uses port 80

The easiest solution is to specify another port for PerformanceGuard to use.

If you found that it's PID 4 that uses port 80, but you want to use port 80 for PerformanceGuard, you must go to Windows' Service Manager (select /Start, type services.msc and press ENTER) and stop the other service that uses port 80. If you do this, also make sure to change the properties of the service in question, so that its startup type is set to Manual, otherwise the unwanted service may soon automatically start again.

Before you stop the service than uses port 80, make sure that the service is not used for important purposes on the computer in question.

If it's the http.sys service that uses port 80, you need to stop http.sys. Open an elevated command prompt, and run these commands:

net stop http /y

sc config http start= disabled

What's an elevated command prompt?

It is a command prompt that's able to execute commands with administrative privileges. To get an elevated command prompt, click /Start, type cmd, right-click Command Prompt in the search results, and select Run as administrator.

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