Win 7 install created new Vista networks

[td650]

I had a network with 2x Win Vista PC's, 1x Win XP PC, and a shared printer.
I replaced the Win XP PC with a new Win 7 PC.
Now the 2x Win Vista PC are on separate networks: Network 2 & Network 3.
The Vista Network 2 PC can no longer see or use the printer, which is cable attached to the Network 3 Vista PC.
Seems like the Win 7 installed new, separate networks for the existing Vista PC's.
The network hardware is: Comcast modem > Dynex router > Cisco ethernet switch > 3 PC's.
I did not change any network connections, hardware or software on the Vista PC's.
I simply removed the Win XP PC, and replaced it with Win 7 PC on that network cable.

 

[MaddogF16]

Check what group the Vista belong to, Win 7 should have been Homegroup as standard. Open menu and right click on computer, then choose properties.

 

[td650]

The 2x Vista PC's belong to Workgroup [the Windows default name], but on separate networks.

They cannot join the Win 7 Homegroup because they are not running Win 7.

Vista "A" PC on Network 3 has a printer attached via USB cable.
I cannot figure out how to put Vista "B" PC on Network 2, onto Network 3.
I just want Vista B to use the printer on Vista A.

I don't care about networking all 3 PC's together, or having Win 7 PC use the printer.