Declanworld, if you can find another power supply with the same voltage and polarity then try that as it could be faulty. Just because the blue light comes on doesn't necessarily mean the power supply's working properly.
With USB powered, sometimes the USB ports can't provide enough power to power the drive properly. Lights may flash, but no one is home. You can get cables that have to USB connectors at the PC end, so that more power can be supplied (i.e. have a Toshiba drive that came with one of these).
If not USB powered. Could be faulty power supply, faulty USB cable, faulty electronics somewhere along the line.....
It's USB-powered and contains video and photos. I've tried it in quite a few desktops and laptops without success. Seagate's troubleshooting area doesn't apparently deal with possibility that the drive is kaput.