When I connect my external USB 2.0 HDD, Windows has an autorun option enabled and opens Windows or starts software.
Do you know how to disable this option for USB devices?
You can try this, but it also disables the autoplay for CD and DVD drives:
Start -> Run -> gpedit.msc
Go to "Administrative Templates" -> "System". Next, doubleclick "Turn off Autoplay", check "Enabled" and select "All drives".
If you hold the shift key down the software in any CD/DVD drive won't attempt to start. If you insert an external drive don't you want it to be recognized?