So I wanted to download and play one of the older versions of MC (Alpha 1.2.6 to be specific) and it instantly crashes outputting the message "GAME CRASH : An unexpected issue has occurred and the game has crashed"
I tried with other alpha versions as well as beta versions, none of which worked.
This issue is new to the new launcher, I didn't run into any problems on the old launcher.
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The game doesn't seem to be outputting any crash logs that I can find.
The versions seem to have downloaded without issue, however on launch, it crashes almost immediately and outputs the game crash message.
Here's an image of the MC game output window after the issue. http://imgur.com/a/b2Nu8.
If there's any other locations I can look or thing I can include to help out, let me know.
The newest NVIDIA driver is faulty, causing Minecraft to crash. The driver in question is version 378.49.
Download the latest driver version 378.66 from GeForce's website.
If that did not help, please use the community support link below.
Quick Links:
📓 Issue Guidelines – 💬 Community Support – 📧 Customer Support – 📖 Game Wiki

Ahh, thankyou for your speedy reply. Updating all my NVidia drivers and such seemed to have solved my problems.
Thank you for your report!
However, this issue has been closed as a Incomplete.
Your report does not contain enough information. As such, we're unable to understand or reproduce the problem.
Please review the guidelines linked below before making further reports.
In case of a game crash, be sure to attach the crashlog from
[minecraft/crash-reports/crash-<DATE>-client.txt|http://hopper.minecraft.net/help/finding-minecraft-data-folder]
.Quick Links:
📓 Issue Guidelines – 💬 Community Support – 📧 Customer Support – 📖 Game Wiki