let's see: your printer is connected to the desktop and both desktop and laptop are connected to the wireless router right?
OK. Here's what you need to do. First you need to make sure your desktop and laptop are on the same network. Can you see the desktop when you go to My Network Places? If you can then proceed.
On the desktop - go to the printers & faxes folder and find the printer. Right-click on it and go to properties.
Under the sharing tab, make sure you check the share this printer button. Give it a share name.
Now, go to your laptop, go to the printers & faxes, and click on add a printer. This will open the add a printer wizard.
Hit next. Then select a network printer, or a printer connected to another computer, then hit next.
Select browse for a printer then hit next. If your desktop and your laptop are on the same network, then you should see the printer name.
Select the printer then hit next. It'll ask if you want the printer as the default printer. Select yes, then hit next. Then finish.
Now... if you don't see your desktop on My Network Places, you'll need to make sure your laptop and dekstop are on the same network first. Under XP, go to My Network Places, then click on Set Up a home or small office network. Then follow the directions, and select a name for your network. Your desktop and laptop should be under the same network name.