Setting up Windows File Sharing

Hi, I hope this is the correct forum for this post, if not, please let me know!

I am attempting to get file and print sharing to work across my home network. The computers connected are:
2 desktop computers running Windows XP Home edition, connected wirelessly
1 laptop computer running Windows XP Pro, connected wirelessly
2 macs, running OS-X, connected wirelessly, one acts as print server

I have a linksys router wireless-G, and Comcast cable internet

As of now, the macs can share files and print
the XP-Pro laptop can access files on both macs
we can see one of the desktop computers (blackdell) from the macs, but cannot log into it.

I know the IP addresses of each computer, and the name as given on ipconfig. And I've selected documents folders to share.

I cannot figure out where to go next. Any suggestons or hints would be gratefully appreciated.

Alisen