I have two laptops running on Vista and XP. I want to be able to print from my laptop to my desktop (Vista) printer but I don't know how.

You need to share the printer, then connect to your desktop to use it..

Go to Start>Control Panel>Printers on your desktop. Right click on the printer and select Sharing. Set the printer up as shared.

Then go to the laptop and from the Printers choose add a Printer and chose a network printer. The printer should appear on the list so you can add it to the laptop.

You would need some sort of device (such as a router) that has printer port on it. This will allow you to share your printer over your home network. Here is a relatively cheap router that will allow you to do this.

Here is a link to an ASUS router with print server functionality... Just do a little research and you can find other great routers or devices that can do this for you

http://www.buy.com/prod/asus-wl-520gu-125m-broad-range-ez-wireless-router-all-in-one-print/206865166.html

You would need some sort of device (such as a router) that has printer port on it.

This is ONLY one of several ways to share a printer over a network. The ways are:

1) Connect printer to a PC and enable sharing
2) If the printer is networkable, connect it directly to the router via an Ethernet cable
3) Use a print server (either a separate device connected to the router via an Ethernet cable or one built into the router or another device).

Well I don't think he has a network printer, and sometimes the sharing option doesn't work the way it should. So I figured the print server would be his best option for this scenario. Sure it'll cost a bit of money, but the router I posted was no more than $50 and it has wireless-N capabilities... So an upgrade may not be a bad option

They also make Wireless Print Servers.
Plug your printer into it and then a wireless connection to your Router.