2008 World Championship for Heroes IV Online.

I don't have a premium Hamachi account – will that be a problem? (Sorry for the noob question, I don't have time to figure it out myself)

You can install the premium version temporarily (it seems like for 30 days). It takes about 1 minute, I installed it myself the other day :)
But it's mainly needed to access the general chat! To simply send a message, the basic version is sufficient, the main thing is that this person is in Hamachi at that time!

Installing MSN is not difficult at all, it's a five-minute job. I recommend Miranda as software because it can work with two protocols simultaneously.

You're right, Oxygen, I went to the link and installed it in 5 minutes :) I haven't worked with MSN yet, but I don't think there will be any difficulties :)