you need to change the workgroup name to match you network workgroup
so in win 7 you need to click on start then move the mouse to computer then right click properties in the window that opens so info and one of them will be computer name,domain and workgroup settings on the right hand side you will see change settings click on it,
system properties window opens and you will see "to rename this computer or change its domain or workgroup click change. then change it to match your network i think you will have to reboot after i hope this helps.