Hello and welcome, Autoharp!
I have Vista on my laptop and no problem using the USB connection. If you haven't already you might want to read the guides posted here:
http://entourageedge.com/support/. The eDGe doesn't sync like a cellphone does.
Are you trying to download epocrates directly from your Pocket eDGe browser?
Edit: I found the free version of epocrates here:
Download Epocrates for Android. I didn't see how to download the latest version, but the 1.91 version might be better than nothing!