I just did a virus scan today and it pulled this one up. Ad-Aware didn't find it but Norton Anti-Virus did.
There is a folder "ETEA" that should be under your "Program Files". This is where Rpen.exe originates from for me. I deleted that file and did a search on my drive and deleted Rpen.exe after cancelling the process. It is finally gone for me. I think it caused many pop ups for me because I haven't gotten the pop ups I was before I did this.
For me the directory path of Rpen.exe was not "ETEA", it was in another folder.