Unless you've got an A500+ (2 MB Agnus) the pinout is always the same.
Most 2 MB slow RAM expansions only work with the initial 512 KB chip/512 KB slow mem config, but this one seems to be fine with 1 MB chip when jumpered appropriately.
The problem with the external drive is pretty strange. The internal is working AOK at the same time? This should only be happening if you connect any of the jumper cables to the wrong pins...
