I have a similar set up to yours 3 pcs on my network including one with win7 64 bit and all can be seen from the mede8er so perhaps I can help. Maasbommel has gone through the obvious things regarding connections so I think your problem will be with the Win 7 shares themselves.
I see you have vista and xp machines in your network, can they access shares on your win7 pc?
Have you setup your win7 pc shares as per Mede8er1 post above but using your login name and pass rather than "everyone" - see my post above
When you go to media library on the mede8er and select network as the source what comes up? It should say:
your network name
sometimes this doesn't appear straight away so give it a bit of time
When you select your network name what shows up - does your win7 pc show up?
If it does, select it and enter the user name and pass you used for the shares on your win7 pc and see if it connects and shows your shares. One of three things will happen at this point:
1 The connection will fail
2 The connection will succeed but no shares will show up, just "return"
3 The connection will succeed and your shares will show up
If 1 or 2 happen then try selecting my shortcuts and setup a shortcut to your win7 pc - there are some details of how to do that here http://www.mede8erforum.com/index.php?topic=47.0
Try this and see if that now connects and shows your shares
This should get you going but if it doesn't let me know the answers to the various points above and that should enable me to sort it out