The below advice assumes you will have a network card in your desktop computer.
The Linksys router you are looking at will work, but as it does not contain an ADSL modem or firewall, so you will have to share your internet connection from your existing computer, and continue to use your existing USB modem. this means that for your laptop to access the internet your desktop must be switched on.
If you wish to go down this route then a simple wireless PCI desktop card will achieve silmiar results. (Assuming you don't want to expand your network any further, in which case the router is best)
However, If you have the money a much better option is to get the Linksys WAG54G 54Mbps ADSL VPN Wireless Router click here
It's more expensive, but it contains both an ADSL modem, and a Hardware Firewall.
What this means, is that you configure your new Modem router to access your ISP, then plug your desktop into the router with a network cable (There's one supplied with the Modem / Router) then there will always be an internet connection waiting for you to use, either with your desktop or your laptop.
I've purchased just such a modem / router and it's fab, easy to setup and use.
Another bonus is that it contains a hardware firewall. Before I had the new modem / router, i was getting around 2-3 thousands access attempts a day being blocked by Zonealarm. Since I installed the new modem / router. I've had none...