maybe a dirty board on the bottom of the drive, try removing it and cleaning the connectors on the bottom and retry to see if it detects. also early 30mb wd drives had a socketed bios chip,the have a flat chip pin inserted into a round hold, fixed a few hundred that didnt detect by soldering the pins (use heat sink on each pin) into the round sockets. You can also just try removing the chip gently,prying it out and cleaning the pins (i bet they are black) a basic pencil eraser works.