I have 3 computers in my network, two running Windows 7 and one running Windows XP. I've set up a homegroup on both Windows 7 computers. Also, all computers are in the same Workgroup.

The problem is that one of the Windows 7 computers makes all shares accessible to the entire Workgroup instead of just sharing to the Homegroup as it should be.

I created the file share in Windows 7 via right-click in the explorer, then click on "Share For" -> "Homegroup (Read/Write)" (translated from German, so the actual wording may be different).

Also, when I look at the file sharing properties of that folder, Windows Explorer informs me that Users must have a valid account and password for this Computer to access drive shares. Unfortunately this is not true. Being in the same Workgroup is enough to get access.

Homegroup restrictions work as expected on my other Windows 7 computer. When trying to browse those shares from the XP computer, I get a dialog asking for a login and password.

What might cause homegroup restrictions to fail and how can I fix this?