My main PC is Windows 7 Pro and I get the notifications about upgrading a few times a week and I just close it out without doing an install. The PC is probably more than 5 years old and I figure by the time Microsoft stops supporting Windows 7, I'll be long overdue for another PC. The PC I have has sufficient RAM to do what I need to do easily.
I have two Windows based (PC) music servers. One started out as Windows 8 (which I upgraded to 8.1) and the other as Windows 8.1. I've upgraded them to Windows 10 with no real significant issues (had to re-install JRiver on both). I basically use only 2 programs on each of the them (JRiver and have started to use Room EQ Wizard) so I didn't see any downside to the upgrade. I have many more programs on my Windows 7 machine and don't want to get into fixing a lot of things when I'll likely start looking at upgrades in a year or so to that PC.
I still have a Windows XP machine (which has 3G of RAM and is plenty fast enough) but since the OS is not supported, I only connect it to the web to update printer software a couple of times a year). I do have discs to upgrade to Vista (I also have an old Vista laptop which sees almost no use) but don't really see the point.
So I'd just close-out any pop-ups you get.