Um...and why would you want to do this?
For restricting memory, you can disable or manually control virtual memory. This does speed up your computer if you don't need more than however much system ram you have, but can cause problems when you actually DO need more(some games do require around a gig or memory!
As for processors, I'm sure there's something out there. I used to have something that let you emulate slower clock speeds to run older games. No CLUE why you'd want to slow it down, but that would be about the same really...