Installing replication services - instance already in use

I am trying to complete my installation of replication services but I am getting an error that states the instance is already in use. I am trying to add a feature onto an existing instance. Of course it is already in use.

Has anyone come across this error and have a solution?

are you selecting the adding feature or installing a new sql instance? Maybe somehow the installing new instance was selected hence it does not allow you to install it again with the same name. Try to post the error screenshot if possible.

Thanks Dennis for the response. I definitely chose to install a feature to an existing instance. Here is the text from the error message.

TITLE: SQL Server Setup failure.
------------------------------

SQL Server Setup has encountered the following error:

Instance name 'my server' is already in use. To continue, specify a unique instance name.

Error code 0x858C0014.

so after not looking at this for a while I am back to trying to get it to work. I didn't notice this last time but when trying to install I noticed that the data directories page is pointing to C:\Program Files (x86)\Microsoft SQL Server\MSSQL12.TRELVSQL02\MSSQL\DATA. But the instance of SQL Server is installed in C:\Program Files\Microsoft SQL Server\MSSQL12.TRELVSQL02\MSSQL\DATA.

I am wondering if this is why I was getting the "instance already in use" error. Perhaps because it was installing it to a different directory but with the same instance name. The problem is if I change the install directory to C:\Program Files\Microsoft SQL Server\MSSQL12.TRELVSQL02\MSSQL\DATA I get an error that says the file already exists.

Any suggestions?