What's ATAPI? and why won't my 200mmx boot with the HDD I've bought, it comes up with the message that the HDD is not ATAPI compatible and displays the message I/O disc error
It stands for Advanced Technology Attachment Packet Interface. It is another name for the EIDE interface on the hard drive. If you have bought a new drive, then it should be compatible. Try disconnecting other IDE devices, CDROMs, other hard drives etc and set the jumper to master and see if it is recognised and accessible.