Things are working.
I got Putty working on com5 and the data logging into a file which is on the PC so I'm just about there.
To make it more complicated I spent the day getting Xbees working so now I can go from the roof wirelessly to the other Xbee on an Arduino next to the slave PC. It may not be the most elegant solution but it does what I need. The whole Arduino setup on the roof is solar powered so no power worries there. The other Arduino is USB powered.
Thanks for all the help.