That's not true - Windows 95/98 will crash on startup if you have more than one CPU core present. You could make it work on Pentium D/CoreDuo/Core2Duo cpus by disabling the second core, but nowadays with modern CPUs there's no option to limit the CPU to a single core. Unless there is some workaround for it that I'm not aware of.
I've haven't seen a bios that would allow disabling all cores except for one since at least intel 2xxx series - there is almost always a switch to disable hyperthreading, but a switch to disable all cores bar one?
