Download Problems

I'm trying to download Serviio onto Win 7. It downloads and when the "Download Complete" message pops up the servio.exe file disappears from the folder!
I've disabled the Avast antivirus and still the same thing happens - Any Suggestions. I'm not a PC expert but consider myself a reasonably experienced amateur.

Do a search for the Serviio.exe file and see if it still there but just in another directory. I think what you are seeing is the file downloaded to a temp directory but once complete it gets moved to a permanent directory under your user. I could be wrong but I have seen that happen before.