Ok, I'm looking at the licence now.
Point 1. It will not apply to you if you are outside the US, no matter what it says.
Point 2. You are NOT using it commercially, you are merely advising someone that this is a good piece of software to use and they agree to you installing it, paying you to repair their PC. At no point are you using the software commercially.
Point 3. If you install it on another machine, it will have a "new" licence. Therefore you are not transferring it, etc, like people do when they use the same serial number for some software on various machines. You don't have a licence when you download the software, all you have is a means to install it. If ou have the full version and share that key and software, then you are breaching the agreement, etc.
Point 4. The licence agreement is just the usual bumf which would not stand up in any court, if you were to use the software in the way you state. You are not breaching the agreement as you are not using or modifying the software in any way that would constitute a breach of the agreement.
So, basically, install it on any PC you wish as long as you are not actually charging for the software but are only charging a reasonable fee for the time you have taken to fix the computer