After flashing with the ASUS trx file, you can change to the generic VINT mini or standard using the Administration -> Upgrade Firmware tab, but whether you do that or not the 802.11a radio will no longer function, either way.
The devs are not interested in getting both radios on this working (Linksys DID release GPL source for this one, but not for v2; only 4MB of flash memory on both), so save yourself hours of frustration and just leave the stock firmware on it. If you're interested, you could salvage the 2 mini-PCI cards (one 802.11b/g and one 802.11a) from the inside... but you have to unsolder the hold-down clips to do that. Also, the swivel/jointed rubber duck antennae are not removable so nothing to salvage there, really. Rubber feet off the bottom, I guess.
In Windows XP, Click Start Button - All Programs - Accessories -
Communication - HyperTerminal
Enter a name for the connection, Click ok
Choose com port you adapter is plugged into, Click ok
Bits per second = 115200
Data Bits = 8
Parity = none
Stop bits = 1
Flow control = none
Click File - Save As, and select a place to save it to so you
don't have to enter the settings again.
After installing putty, run it
Serial line = The COM port your using for serial (ie. COM3)
Speed = 115200
Click on Serial under Connection
Serial line to connect to = same as above (Serial line)
Speed (baud) = 115200
Data bits = 8
Stop bits = 1
Parity = None
Flow control = None
Enter a name for your connection under saved sessions