U can't replace the CPU of a laptop.
Of course you can. I'm doing it on a Thinkpad right now.
The problem is that I now have 815,944 microscopic parts scattered all over my desk that will have to go back in the right places. In addition, because the OP is working on a P-II class *Compaq* system you must assume proprietary parts that will break due to age as soon as they are manipulated.
Long story short, that laptop isn't worth upgrading in even the smallest way. I wouldn't buy a can of air to clean off the keyboard for that system.