OK, I can see a clear progress. The last time I've tested two X1900's Pro AGP versions and none worked. This time none worked, BUT in one case I was able to see my desktop... for about 10 seconds and then everything hang. Then I couldn't reproduce my success any more, no matter how much I've tried. What is more interesting - that (partial) success happened when I was running a gfx card that PC failed to initialize. The one that worked like a charm in a PC didn't show me anything. Even the fans didn't spin to a higher speed (like when the system boots).

Moreover, when I put back my X800XT, computer started to misbehave. The mouse coursor refused to move, CPU temperature upped to 95 degrees Celcius... Had to remove it, unplug everything, clean the AGP slot with some air and now it looks like it works again. I'm a bit scared to do another try today, so let's call it quits, OK? I'll go and find some better powering cable than from a DVD molex and then... maybe... I'll dare to do it again. Hopefully.