can't share printer with Vista

Hello,
I have 3 PCs Wi Fi two with Vista Basic and one on XP Family my provider is
WiFi too, I have my wifi network called "pat" it gives me internet on every
machines and it is my local network too (definedublic)(internet and local
network)
My Pcs are P1 Vista,P2 Vista, P3 XP
the printer is plugged in an usb of P1 and defined shared.
From P1 I see P1 and P2 and their shared media but not the printer
From P2 same thing for P1
And when I try to look in P1 from P2 and vice versa I have the same error
message "don't find the path"
And the printer is not on P2 too
And the same problem with P3 and I don't see the shared medias from P3 about
P1 and P2 and the printer.
I have tried many things but don't understand.
I have tried to search explanations on the net but found nothing.
If you have an idéa please because same shared folders I can't see from
PCs!!!!!
I have headache!!!
I thank you very very much if you can help me about ,give me a link, or show
me the way or explain to me.
Thank you again
Patrick