These old slim Maxtor IDE 20 & 40GB hard drives are prone to start up problems. When they fail, it sounds like a mechanical problem as the heads cannot settle and make a clicking noise. They also do not show up correctly in a computer bios. This generation of Maxtor disks are known for firmware corruption, which is usually the fault.
We have just received one in for data recovery with the usual failure. With our past experience we have been able to overcome the problem without having to open up the drive in our cleanroom.
Maxtor has been sold to Seagate so if you need data recovery, have a look at our Seagate Data Recovery Services.