Hi

I have just installed 'Back to the future' on my fairly modern laptop, but the game won't even start. I have tried to run it as administrator, and that was the only good idea I could get.. any suggestions?

The laptop has these specs: i5, dedicated graphics, win7 64bit

For your laptop shouldn't be a problem running this game, indeed a lot of people can't launch the game. Try to search for a solution on the official forum of TTG, there are various threads that can help you, like that http://www.telltalegames.com/forums/showthread.php?t=21413 .

Someone for example suggests to install all the episodes, then trying again to start the first one.

In my case the game didn't start until I removed the gamepads from my PC (Windows 8 64 bit).

wow removing my game pad actually worked thanks

This is a known issue for all (older) Telltale games, Microsoft changed a DirectInput dll in Windows 8.
It's also possible to exchange the dll with an older version, but removing the gamepad is the most common solution.