pirated windows 7 installs?
I guess they'll be pretty upset when Windows 8 comes out then.
That said, my parents have been using (Ubuntu) Linux for the last 5 years without any problems at all. It's definitely reduced support calls from them (no more crashes or viruses). They're still using the same old PCs from when I first installed Ubuntu. When I visit them, I install a new LTS release, if it's available (one's released every 2 years), a process that takes about 30 minutes of my active attention.