Download PRSP_505_2.0.17rc3.zip PRS+ 2.0.17 release candidate 3 for 505
from
here
Unpack it, you should get a Folder "PRSPInstaller", with a sub-structure as shown in dwanthny's post.
A) Connect our PRS-505 to USB, copy mentioned Folder to the reader
(Just the root of the removeable media shown in Explorer/Finder)
Eject USB media, Installer should show up.
B) copy folder to a empty SD-Card,
insert SD-card into your PRS-505
again installer should show up
Good luck