The one instance where the other tech thought it would be okay to use "XP mode" the PC was used ONLY for driver/apps for a CNC laser, they're shop was down for a week when it errored rather than just having an XP installation and knowing the fixes he had to diagnose it. I don't know the details, other than he can be pretty dumb sometimes. I've never used the XP compatibility stuff myself.
Although why use an OS that is so much larger, for single task systems such as that? Waste of resources.
Not all processors support x64. A processor that won't handle Windows 7 in your eyes might be "fast" enough for someone who cares or knows less about performance and requirements. If you argument there is if it's that old don't install Windows 7 on it I'd have to agree though don't get me wrong.

