Networking with Win 7

[Scientific]

I'm having major problems sharing files between computers. I have 3
computers. The first two are running Win XP and the third is a laptop which
came with Win 7 Home Edition installed.

I can't get my laptop (Win 7) to connect with the Win XP machines in order
to share files. My laptop doesn't see the XP machines, but the XP machines
can the see laptop just fine. I'm new to Win 7 and haven't figured out the
new features yet. What a nightmare this had turned into. Win 7 doesn't seem
to be backward compatible with XP, I could be wrong though.

Any help will be greatly appreciated.