I just wanted to sing the praises of Estrongs file explorer over Astro. When I first got my droid, I read everywhere that Astro was a must have program, that it was the best manager, etc etc. I honestly wasn't overly happy with the program for some reason and went in search of another file manager.
I stumbled across Estrongs and I have to say it is definitely amazing. Not only does it have a much nicer display mode (details!), but it has a zip feature, and best of all, it allows you to connect to your PC's over wifi and transfer files. Just put in the ip address of your networked PC that you want to access, then the PC's username\login and you're in. Worked like a charm.
Give it a try!