Is that Windows 7 SP1? You may need to alter permssions under Firewall > Internet Connections for Programs (takes a while to load and if you click the word Program at the top of the list it will rearrange alphabetically).
If you are sharing with another computer or gadget you may need to add it to the My Network Connections list, also under Firewall, also make sure Windows File Sharing is checked under Ports and System Services.
Technical Support are probably best to advise you on this, it's free of charge by phone or online chat and available via Useful Links at the top of this page.
Or post at Apple Forums to see if others have any ideas: https://discussions.apple.com/community/itunes/home_sharing
I do have iTunes but don't use Home Sharing I'm afraid.
Yeah Window 7 SP1. I have gone into the programs list in the firewall and iTunes is listed as full access. Should Net Guard be on or off? No idea how I add a gadget to My Network Connections.
This all used to work fine until the latest release of MTP.
also - the Windows File Sharing is checked under Ports and System Services is ticked
I'm not too au fait with adding networks either. Technical Support are better at this. Normally networks are added automatically as needed anyway.
As far as Net Guard is concerned you could try turning it off to see if that helps.