I'm in a charitable mood, so I'll save you before you get yourself in trouble jalwaak.
Simply copying the folder over to your new computer isn't the same thing as installing DesktopX from scratch. When you install software, certain information is stored on other parts of the computer which is vital to make the software run. The only way to make sure all these things are present is to do a full installation.
There are three possible ways that your brother could have obtained the software. He could have downloaded the free limited version, bought the full version, or obtained an illegal full version from somewhere online.
If it was the first option, you should just be able to d~e~l~e~t~e that folder you copied across and download the free version again. You should then just be able to install it afresh on the computer.
If it was the second option, when he bought the software he would have been given a serial number (a bit like a unique membership number) and a special version of the software to download. You'll need both of these to get it up and running again. If you think this was the way he originally got the software, then check what his e-mail address was at the time and get him to send a request to Stardock for a reminder of his serial number and a place to download from.
If it was the third option, and he someone obtained the full version from somewhere without needing a serial number, then you're in a bit of trouble. There are illegal copies out there which have been altered to bypass the serial number protection, and someone with the right knowledge could get hold of this version. It is illegal to own or use this version, and my best advice would be to d~e~l~e~t~e the folder from your computer and look into the possibility of purchasing the legitimate version from Stardock.
The reason you were criticized for asking for someone else's serial number is because a serial number is unique to an individual when they buy the software. They alone are allowed to use that number, and it is illegal to give that number to someone else. Generally people who ask for serial numbers are those who do not wish to buy the software, but have someone managed to get hold of the normal full version which requires a number to install. I'm not saying that's your intention, but just be aware that asking for such things is considered a very bad thing here and could get you exiled (banned) from the site.
If you're unclear about any of that, just ask specific questions and we'll try to answer. We were all new at computing once, and it takes time to learn how it all works.
By the way, it's probably best not to call someone who's trying to help you a 'geek'. You'll find that many of us here do have social lives and a few don't even wear glasses which have been fixed together with tape.
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