Hmm, I recognize this.
I have been involved in cases when Windows "somehow" corrupted the system partiton and when installing Windows again, despite formatting from the setup menu, it will with some time keep corrupting the partition, unless you do a low-level-format of the harddrive it self before doing a new installation. That is, using a manufacturer tool to wipe the drive clean.
Since you have not installed windows yourself I can not recommend you to do this, but you could ask the guys at the computer shop if they can get SeaTools
and make sure the harddrive is 100% clean before doing next setup, unless you may want to do this yourself.
They may of course tell you that you are questioning their professional knowledge and tell you that "of course we wiped the drive", so be a bit diplomatic when asking. I have been doing stuff like this for 20 years. And so has many others on this forum.