A nice scanner to use to perform you task is called AngryIP Scanner. I have used it since it has been released and it has yet to fail me.

http://www.angryziber.com/ipscan/

Also, you can put in ports to scan with this little guy. Typically when I look for default print servers I scan for ports 21,23 and 80. This is not foolproof but certainly effective on small LANs.

--TH13