Windows 10 is A Mess→

Ghacks:

You may experience the issue if the count of all Start Menu items exceeds 512. This may sounds like a lot but if you take into account that items are any file, folder or shortcut listed in the Start Menu, is quickly turns into a wider issuer that users can experience.

Long story short, if you get more than 512 items in your start menu, you can wind up with errors ranging from ‘it takes 15 seconds to open the start menu’ to ‘clicking the start menu button crashes the computer.’
Having just spent 45 minutes trying to get OneDrive working on a computer after upgrading it from Windows 8.1 to Windows 10, I’m going to go ahead and say that I’m very happy my main computer is no longer a Windows machine. Microsoft had some good ideas, but they sure as hell didn’t execute any of them.