I'm using vista home premium, what I have done is I convert my csv files to garmin gpx files using POI Edit for Garmin.
I put these files into 1 directory, then using POI Loader send them to my SD card in my nuvi760.
I had similar problems in trying to install the POI Uploader. In the end I merely transferred the file to the Desktop and ran it from there. It then installed perfectly. I have Vista Ultimate 64 bit.