i have a 1.83 GHz Intel Core Duo and want a Core 2 Duo, is there a free upgrade i can to on my mac os x 10.6.8 snow leopard?
More aboutcore upgrade
If your asking if you can unlock a core (which is AMD only anyways) and run it as a dual for then no you can't. You may be able to upgrade to a new CPU though that would have to be the same socket and would cost money. Unfortunately with OEM equipment you can't overclock either so you're out of luck.
If you know what you are doing, and if you can get the right processor, you can upgrade *some* Apples from Core Duo to Core 2 Duo; but you're going to have to give people far more detail than a "mac" to get any form of detailed answer.