Why won't Minecraft open on Windows 10?

Unfortunately your PC may not be able to handle it. As simple as Minecraft looks, it is a very CPU intensive game. Now you said it has 2x2 GB Ram, Having a lot of Ram does not mean you can run a game. It comes down to your CPU and GPU, which I believe the Dell Optiplex 755 is lacking in terms of power for anything other than simple browsing and word processing, that and it uses an integrated graphics chipset which usually aren't built for gaming.

Usually game demos are very watered down so they perform better than the full product, but you can try some simple steps such as posting an error log to the Minecraft forums or installing a performance saver mod called Optifine.

You didn't post what kind of video card you have. But I'd wager you don't have one capable of pulling the game. That is likely why it's telling you to update your drivers.

Then again, it could indeed be a simple case of your video card truly being out of date.

When you say your card's drivers won't update, what does that mean specifically? Did you go to the manufacturers's website for the driver? If you didn't that's the best way to do so… You'd go directly to the manufacturer of your video card (for ex: NVIDIA, ATI, etc, whatever you have), find the driver update link, find your model, and download then install the update.

It's also very possible that your video card does not have a Win 10 driver update available for it. Video cards have been a major issue with Win 10 because a lot of video cards on the Win 7 computers that were upgraded are old and the manufacturer didn't release a driver. IF IF that is the case then it means you won't ever be able to upgrade your video card for Win 10 and you won't be able to run games that need an upgraded Win 10 driver.

I have been having trouble with minecraft and I can't launch it.
Any idea why?