Can I Upgrade my CPU in my Lenovo Thinkpad T400?

I currently have an Intel Core 2 Duo P8400 and I want to upgrade to an Intel Core 2 Duo E8435 or an Intel Core 2 Duo T9900. Is this possible, or will I just ruin something? I have read that someone was able to change the stock CPU to one from a mac. If neither of these work, what should I get to upgrade my speed to at least 2.8 GHz?

Laptop CPU are not inter changeable like a desktop computer. The memory and HDD are about the only thing that can be upgraded.

Usually most people do not upgrade the cpu because better off to buy a new one than to have it install by someone. That would be fine if you are able to do it yourself. Or you can overclocking your cpu. It is not recommended. Hope that helps.