Back in the days where big arse tower air coolers were rare, and wc'ing was even rarer. Oc'ing was more tricky than 3 simple changes in the bios, the thinning or even removal of the ihs to give either a better surface or a direct contact was a good way to shave 5-10 degrees... Usually made a difference in being able to clock ur cpu to 2.4 or 2.7ghz
.. these days ? U can keep ur ihs as-is, keep ur warranty intact, and get a really good cooler. Wc or air. And most new cpus do 3.8-4.2g without crying.
I would say tho, if u had a disposable AMD K7 mobo and cpu, u could give it a go. Even an old Pentium 4 setup. If u don't care if the thing breaks, it'd be an interesting venture.