The mid-2007 Mac mini (model A1176) was a very interesting update for the Mac mini, because it got upgraded to a Core 2 Duo processor. There is however one thing that should also have been upgraded, but wasn’t (for some strange reason – cost reduction ?) : the AirPort card ; that stayed a WiFi-B/G compatible one only… even though all other Macs had WiFi-B/G/N at that time…
Luckily it is possible to upgrade the AirPort card to a WiFi-N compatible model.
I found one for a relatively good price on Amazon.de : the Atheros AR9280. Both MacOSX 10.6 Snow Leopard and MacOSX 10.7 Lion recognize it as a genuine AirPort-N card, so in 10.7 Lion the new AirDrop feature is also supported.
I used the installing directions from iFixit.com :
It works perfectly, even with only one antenna (FYI : normally a WiFi-N card should have 3 antennas, but the WiFi-B/G card that was originally installed came with just one…)