I am running Windows7 and Ubuntu on my computer. I would like to download only one set of data files for both operating systems, so that whatever OS I boot into Boinc will operate upon that data set. How do I accomplish this?

Please bear in mind that I am a complete novice in Linux (I can't even find drive C: in my Home Folder yet), so any explanation will have to be at the level of a simple child.

Not possible, I am afraid. The files that re downloaded are OS specific or at least enough of them are that it isn't possible. I asked a while ago when there was no work available about the possibility of transferring tasks from a windows machine that had spare ones to my linux machine and was told very clearly that it wouldn't work. Don't worry about the time it will take to complete models because of this - work is still accepted and used after the deadlines.

Dave