Is it possible to upgrade Presarios?

A friend of mine has a Compaq Presario 5600i. He wants to make it a little faster. He was thinking of a video card, since it only has PCI slots, I suggested a PCI card with the nVidia chip. But he would probably see a bigger improvement if he upgraded his processor. Currently it's a Pentium II running at about 400-450mhz.

Can the CPUs of this Compaq be upgraded? And to what speed can he upgrade to 900mhz, 1.2ghz?

Plus can he move to a Pentium III?

I myself don't know too much about things like this and so I'm hoping someone who knows much more about this can really help.

only thing worht upgrading on a compaq is the memory, and not even that worth it. if he's considering upgrading make him save some mroe money and build himslef a computer that will ahve a continual upgrade path. but if he insists on upgrading, an invida geforce from an integrated vga card would do more justice than a few hundred megahertz.

repeat after me, we are all individuals!