Unity 5 and unity 4 at the same PC?

Hello!

Well I was wondering, can I download unity 5 but still have unity 4 at my PC?

In other words do I have to upgrade my unity 4 project but make a new one with unity 5?

Yes you can have both. I have both installed now and use it to compare while I work through issues upgrading my project. You should definitely copy your unity 4 project and open it in Unity 4 from there. Do not share project folders between versions.

You can keep Unity 4 and Unity 5 on the same PC.

You don’t have to upgrade your Unity 4 project unless you want to use it in Unity 5.