Cannot Share Printer / No ping response

WIN XP, SP2 Home. PC is on a lan at local non-profit org. PC in question can access internet,shared files & printers on other PCs. Have setup local printer to be shared, but it cannot be found from other PCs, and this PC does not respond to PING except from self. Have turned firewall off w/ no effect.
When I try to search for printer from other pcs, it is found, but when I select it from list, I get “Bad Printer Name” and am told printer cannot be found.
I have tried running Knoppix from CD and when Knoppix is running, I can ping the PC, so problem appears to be in WIN XP.
Any ideas?