Minecraft has stopped working, what to do?

My Minecraft has not worked properly for a while, if I want to start it then it hangs while loading. I then heard from a friend who would switch Minecraft to Windows Vista in compatibility mode and it would run. It could then be started again, but I couldn't change the language and I couldn't see any more skinns, neither mine nor that of others, all were shown to me as steve.

does anyone know how I can fix this?

Create a new installation with the latest version using the menu above and play it.