Xp laptop to windows 7 desk top

Hello,
I have DSL connection with wireless. I have a new desk top with Windows 7 plugged into LAN. I have a laptop with Windows XP with wireless. I have a printer connected to my desk top. I have the printers driver in my lap top too.
What I want to do is to be able to print from my lap top through the desk top and wireless connection.

I had an older desk top with Windows XP and a techie got it to print through my desk top but since I changed desk tops I cannot get it to work and I lost the aid of the techie.