I 2nd that, for regular usage, Zorin is great OS.
@Gachr I wouldn't recommend Zorin OS for general use, but, for his parents, they (I assume) don't play games, as he said, open browser and enjoy, so, i would recommend Zorin OS over Mint for that. I use Mint as my main system, so no hate for Mint ;).
zorin os is stable enough for the general user out the box. its just buggy when you try to push it but for emails and documentation I've had no issues.
Lubuntu, or kubuntu. Or mint KDE those are my suggestions
it depends on the hardware specs but Linux Mint Cinnamon with Configurable Menu applet can look similar but work exactly like the Windows interface. Configurable Menu has a prebuilt Windows style layout that you can easily switch it to.
Another option is to use Kubuntu. You would need to modify a few things but Kubuntu can present the Windows feel very well.
Disclaimer: don't use any boutique distro for him because they will not have very good support at all. Zorin is an example of that. They claim to look like Windows but they really don't and unfortunately it is also very limited in support and functionality.