Can't see Extra Hard-drive somtimes

[kapow]

I have an external backup drive which I turn on occasionally. Sometimes XP recognises it and sometimes it doesn't. When windows doesn't see the drive I switch it off, wait a few minutes and turn it on again, then usually it works. Sometimes I have to do this 3 or 4 times.

Can anyone tell me why XP doesn't recognise it every time? Is there anything I can do to tell Windows to see the drive?

[longen]

Is it USB or Firewire?
It doesn't appear under "My Computer" when you switch it on?
Are all cables properly secured?

Try clicking
Start>
Control Panel>
Administration Tools>
Event Viewer>
System

Look for Yellow or Red warning messages for clues.