This sounds more like a linux issue than a windows one. Have you tried connecting to the Ubuntu machine via IP? Also if it's a network share you need to connect to, make sure you have samba setup https://help.ubuntu.com/11.04/serverguide/C/samba-fileserver.html

I setup am Ubuntu 10 box the other day on my home network. I can see and access the other devices on the network from Ubuntu but I cannot see the Ubuntu box from any of the Windows machines. I am running Win7 on one laptop and Win Vista on another. Same results. Network sharing is turned on. Any ideas?

This sounds more like a linux issue than a windows one. Have you tried connecting to the Ubuntu machine via IP? Also if it's a network share you need to connect to, make sure you have samba setup https://help.ubuntu.com/11.04/serverguide/C/samba-fileserver.html