OK, not classic Opel Related but here´s a link to a page that sells a OBDII interface for diagnosing 1996 and newer vehicles.
OBDII Interface Home Page
This great unit plugs into the OBD (On Board Diagnostic Computer) plug in your vehicle and the other connects to a laptop or desktop pc. The program is so small that you do not need a harddrive. The cost is only $76.00!!! They even sell kits for the Do-It Yourselfer´s.
I picked one up a few months back and recently used it when my Tacoma´s check engine light came on. It a matter of minutes, it pulled the code and said it was the front O2 sensor. I ran further tests comparing both O2 sensors voltage output. It even plotted the timing advance. It reads whatever is in the car´s computer just like the $1,000 units.
There is a simulated demo program in the free software that is available on the site.
My BR-1 Interface has already payed for itself!