Guild Wars 2

I’m having trouble upgrading my existing account to Heart of Thorns. When I open the Computer tab, hit the disc icon (with HoT in the drive) and hit setup it opens my regular game client which doesn’t update.

You need to add the serial number to your account info. You don’t need the disc at all, if you have been playing you already have all the files needed.

Make sure that you applied the HoT registration code to your account, but your GW2 client should already be ready to go. The ability to access the Heart of Thorns content is just verified withing your account having the proper registration code.

How do I add the code? When I hit add code and type in the serial code from my manual it is in the wrong format. For example, it says it must start with a 6 character batch but mine reads 5

You need to be at ‘My Account’ in https://www.guildwars2.com/en/services/ which I think you are…
If you bought your copy from a reliable source, contact support about this strange serial code. Actually, you probably should contact them anyway, they would probably want to know if there is something fishy about the place you bought yours from.