I have a PC running Windows XP and an iMac running Mountain Lion.
I turned on Home Sharing on both using the same Apple ID.
The iMac saw the Windows files right away, but the Windows computer does not show the iMac iTunes Library in the sidebar at all.
How do I fix this?
The following article(s) may help you.
In particular look at firewalls and security software on your PC as possible culprits.
Retrieving data ...