X3550 All-In-One Printer: Can this printer be converted to wireless?...

Configuring the optional internal wireless print server
If you purchased the optional internal wireless print server after your printer was already set up, follow these steps:
1 Install the internal wireless print server into the printer. For more information, see "Installing an optional internal
wireless print server" in the "Setting up the printer" chapter.
2 Click Start Programs or All Programs Lexmark 3500-4500 Series.
3 Click Wireless Setup.
4 Click Start.
5 Follow the instructions on the computer screen.
6 Click Finish to complete the installation.


Also here is the link to the setup guide and user manual
click here

configuring the wireless is in the setup guide

Try E-Bay, you might be lucky.
Failing that, you can try using a LAN print server, connect the printer to the print server and connect the printer server to your LAN.
Then any computers on your LAN can print to this printer.
OR
Connect the printer to your computer and set it up as a shared printer and if your computer is connected to the LAN then any computer can print to this printer provided you computer and printer are switched on.

If the printer is using bluetooth then get the laptop activated with the bluetooth with the same passkey ... get the printer and laptop to activate bluetooth -- open bluetooth manager and select device then put in the passkey in both the sets to communicate.
Now you have the printer connected and can send your documents for printing.

Reset the Network Adapter of the printer by pressing the Settings button on the Operator Panel on the printer> Network Setup> Wireless Setup> Reset Network Adapter to Defaults> Yes. Reinstall/reconfigure the printer for wireless connection. Make sure you are using the correct wireless network information and that the computer belongs to that network. Hope this helps. If you need more assistance, leave a comment and I'll get back to it. Thanks.

If you are trying to connect to a network printer you need to install a network printer NOT a PC install. You would have to browse for the "Remote" printer, from the CLIENT. The printer that is on the "Master" PC will have to have the printer already installed and "shared" as well, FIRST. Then you go to the remote and install a NETWORKED printer....find it on the network, and connect, it will actually get the drivers from the "Master" PC, see. Plus BOTH PC's will have to have a name password & and be on the same "Workgroup" as well. If you want to enable documents to be exchanged to print between PC's you will have to enable "Sharing" on each, Drive, or Folders as well, if you wish.
Tutorial here http://www.online-tech-tips.com/windows-xp/how-to-install-a-network-printer-on-your-home-or-office-network/

well considering the x3550 isnt a wireless printer you cant

http://www.provantage.com/lexmark-14t0300~7LEXP0M5.htm
Yes you would have to purchase the plug in module.
Thank you,
Lee

This is probably the Software Firewall on your laptop

you should probably tell your firewall software that you have an internal network (Laptop-desktop-printer) you should add the IP range of the wireless network as a trusted network.

The 34 and 35 cartridges will work. You can also buy a 23a or 24a from Lexmark.com and you can refill those.

I think you can use this wireless card, not sure which printer models it works with though.

http://www.lexmarkonline.co.uk/product_info.php/tab/Customer_reviews/info/p449_Lexmark-N2050-802-11b-g-Wireless-Network-Card.html#tabs