Windows ME users would like to have a serious discussion with you.
I'm holding out until I get a new machine. My laptop is four and a half years old (and replaced the hard drive December last year) so while Windows 10 SHOULD run well on it, I don't see the sense in installing a O/S over the top of an old one (I'm more of a fresh install kinda guy) onto a older machine.
Plus there will be things they'll have to sort out.