Assuming that you are in a cabled area and get your broadband service via cable and a cable modem, then what you need is a cable wireless router.
Just make sure you don't buy an ADSL modem/router.
I can recommend the
Linksys WRT54GS as this can carry even the 20mbps Virgin service.
If your desktop is close enough to use a cable then do that. That router like most has four ethernet ports available. Wired connections are faster, more reliable and more secure, although obviously lack the convenience.
The router will need the security set up when you get it, but it's pretty straightforward.
regards
Brian
EDIT the GS is out of stock with Amazon today but the
GL is available which will also do fine