Access denied due to security settings. Either change the permissions on the Program Files folder or put the RTDStore app in a different folder.
For the author: downloading into the app's working directory is, and always has been, a terrible idea. That's why Application Data and Downloads and Temp folders exist...
Win8/Windows RT projects:
List of desktop apps for hacked RT devices
Native Access WebServer and Libraries
WP8 Interop Unlocks
Storage Cleanup tool
XapHandler, Root Webserver, OEM Marketplace XAPs, Bookmarklets collection (Find On Page), Interop-unlock hacks.
Do not private message me with questions that should have been posted on the forum!
Not only are you wasting your time - I'm not going to bother writing an answer to such a question for only one person - but I will probably block you from PMing me in the future as well.