Well, for unricking when NOTHING shows up anymore, you need the Cradle, a parallel cable (wired-through, nothing fancy) and a serial cable if you want serial output (not needed, but you can see what happens).
This works for any unit from F100 First Edition up until F200. It does NOT work with F200 (B) yet.
Then you need the
software for unbricking and a firmware (2.0.0, 3.0.0 or 4.0.0, not minor numbers).
You extract the firmware onto the SD Card and put the SD Card into the gp2x.
Then you put the gp2x in the cradle, turn it on and start gp2xrecovery.exe.
gp2xrecovery should find a gp2x, load up a special bootloader and starts that one when finished uploading. (If it can't find a gp2x, the dosbox window immediately closes. Check your parallel cable, ensure the gp2x is switched on. And it's best to start gp2xrecovery immediately after switching on the gp2x).
After the upload has finished, you can see what happens using the serial out. If you don't have serial output, wait about 60 seconds, then switch the gp2x off.
Switch it on again while pressing START + SELECT (HOME + SELECT) until "upgrading firmware" appears.
If you only see the bootloader screen, you didn't press long enough (or have removed the SD Card).
If the screen still stays black, the recovery didn't work. Maybe you forgot the SD Card or didn't have a gp2xboot.img on the card? Maybe you didn't wait long enough? Check this and try again.
That's it.