Hi There If everything was working before you installed the second drive the only things I can think that it might be is you have pluged the connectors into the wrong drives the one on the end of the cable should go to the master and the middle conector is the slave (normally). If that does not work I would try installing the new drive on its own and see if that works, the drive will act as a cd rom so you can install your software or dirvers. also try a different cable if you have one. On some older cables I have they do not have a locator on the plug so you can plug them in the wrong way round I would also check for that and recheck the jumper settings on the drives some of the diagrams can be easily misunderstood depending on which way round you are holding the drive. Hope this helps.
Tony B.