I know of some ten year old machines running critical SCADA control software on top of Windows 2000. Those machines were never intended to be upgraded. They're

I know of some ten year old machines running critical SCADA control software on top of Windows 2000. Those machines were never intended to be upgraded. They're not even connected to the Internet, so I'd be surprised if they've even been patched. They do their job with no fuss, so don't touch them. They're approaching the point where the hardware could start failing any day now, so they're on an upgrade path. This path is, not so surprisingly, very expensive and fraught with politics about how the replacements should be connected to the internet (hint: they shouldn't). These things tend to happen a lot, we just don't hear about it very often. Hell, where I work we're still running CentOS 4 on the vast majority of machines because we know it works.