Win 8.1 file sharing

I have win 8.1. , win 7 and win xp systems running

I can't get the win 8.1 system to see any of the win xp systems on the home network; I know i have to have a home group set on the 8.1 system but I am stumped as to why the two systems cannot see each other on the network.

Could really use some help

Bruce