Unable to play coop with 2 controllers

Hello,

I have 2 controllers to play on PC:
- A very old Thrustmaster Firepower Dual 2 (something like that)
- A Madcatz xbox-like

I used them a while ago to play Rayman Origins in local co-op, no problem, everything went very well, I never had issues with these controllers.
But a few weeks ago, I wanted to use these 2 controllers again to play other games in co-op, but I can no longer play with both at the same time... I can only play with one controller at a time.

I tested both controllers independently, they work perfectly. It’s only when trying to play with 2 that there is an issue. They are both recognized and listed in "Device Manager" and "Devices and Printers", without any notable problems.

The only difference that comes to mind for my computer (it's the same laptop I used to play Rayman without issues) is that I switched to Windows 8.1, while I think I was on Windows 8 before. But I don’t really see how that could affect anything...

Does anyone have any ideas?

PS: I wasn’t sure where to post this message, I also posted it in the video game forum...