I'm just unable to use my (very) old game pad, a MS Sidewinder gamepad pro... on my (very) old Win XP PC...
It's not recognised by this game ! (and just this game !)
Any suggestion ? Buy a new controller ?!

Unfortunately, the devs of SteamWorld Dig implemented their gamepad support very specific for every single gamepad, instead of using a general interface that works for all. They stated that they only add devices they actually own, to map their keys manually to fit the game's requirements (see here).
If your device isn't included, they suggest to work around by using mapping software (e.g. JoyToKey) and map the game's keyboard controls to your gamepad.

If you don't like that approach, your gamepad could be recognized if you use an XBox360 controller emulation tool (e.g. x360ce. Then the game thinks you've got an XBox360 compatible gamepad plugged in, while you're still using your MS Sidewinder.

Thanks for the answer, i'll look at the JoytoKey software first !


Edit : JoytoKey don't work well for me, so i use AutoHotKey : my old SideWinder gamepad is always alive ! and i can use it now in SteamWorldDig.
Thanks again for the suggestion...