Apple on Tuesday started selling the $1.99 software that lets Mac users connect to faster, longer-range wireless networks, fulfilling a promise it made two weeks ago to charge for the enhancement.

The download, available at the Apple Online Store, activates the 802.11n wireless hardware in most Intel Core 2 Duo- and Xeon-based iMac, Mac Pro, MacBook, and MacBook Pro computers.

Apple has justified the $1.99 fee as an accounting requirement. Tuesday, Apple declined to comment on whether such fees would be levied for future enhancements to its hardware or software.

"The $1.99, however, is a site license [fee]," says Jai Chulani, senior product manager of Apple's wireless access point hardware. "You can install it on any Mac that you have." Previously, Apple had not made it clear whether the charge was a site license or a per-Mac fee.

Also on Tuesday, Apple shipped the AirPort Extreme, a new $179 wireless base station that it launched Jan. 9 at the Macworld trade show. The software needed to turn on 802.11n is included with the station.

Like older Apple wireless access hardware, the AirPort Extreme lets users share a USB printer over the network. New to the Extreme, however, is the ability to jack an external USB hard drive into the network, and then share its storage space with both Mac and Windows systems. "The AirPort Extreme can even be set up so that the hard drive automatically mounts," Chulani says.

When the 802.11n specification is finalized, users may be able to update the AirPort Extreme's firmware by going online, Chulani says, although he made no guarantee.

Apple's head of worldwide Mac marketing, David Moody, wouldn't comment on when the company plans to start shipping the 802.11n drivers with new Mac machines.

Editor's note: A change was made to the second to the last graph on Jan. 31 to reflect that Apple is not promising that a free upgrade will be available online once the 802.11n specification is finalized.