Don't worry; your English isn't lousy.
You couldn't have destroyed the Memorex with a firmware update if you performed the update while the Memorex was not installed.
I deinstalled the cd and installed my old drive (Memore MAX 1648) at the same position (primary slave). From this moment on the select light of my hdd was cont. on and I can not access to the drive. I tried several combinations (Memore MAX 1648 as secondary master or slave). As soon I insert the IDE cable in the Memore MAX 1648 the light goes on at the hdd.
Are you re-connecting your IDE cables with the computer turned on? This can potentially damage the drives, and the computer might not recognize the drives right if you do this. You should at least turn off the computer before changing drive cables, and optimally, you should actually unplug the computer from the power socket.
If you are changing drives while the computer is running, try turning it off for a few minutes and then turning it back on again. This might help the computer to recognize the drives correctly.