Workgroup browsing requesting password

I have a peer to network with 2 xp home pc's and one windows 7.

everyone can see everyone when I select View workgroup computers.

But when I double click on a PC it asks me for a password.

With the 7 machine it asks me for a username but with the xp machines it assumes a username of pcname/guest

the pc's are password protected but the usernames are not guest and it does not allow me to change it. none of the passwords word and leaving the password field blank does not work.

I have never come across this before.

hopefully somebody has and can help me out here.