Try using a slowdown utility, like <a href="http://www.oldskool.org/pc/help/oldonnew/resources/turbo.zip">Turbo</a>, or <a href="http://www.cpukiller.com/">CPUKiller</a>.

They work by creating a high-priority thread that pretty much chokes your CPU, so don't set it too low to start off. Try a high percentage first, like 75%, otherwise it'll lock up.