Why would you want to run slower? Retarded!!! Fail!!
Well that's not nice at all...
TBH, I actually underclock for the fun of it. I underclocked my GPU to reference (675MHz) just to see how silent it could go, and it was amazing. CPU I want to try still, see how cool I can get it with my Hyper 212+ cooler.
Dude that's something else I can try before I upgrade! Cool idea! Also, underclocking is something I'll recommend my friend, who has one of these extreme Asus ROG i7 gaming laptops, paid like $5500 for the thing. Run so hot, the exhaust air literally burns you when you hold your arm against the exhaust. It's incredibly hot, never thought a laptop can get that hot!