Sorry I threw in a typo, I'm working at the same time. You very well knew what I meant.
I don't ever remember "insulting your quiery", just giving my opinion on what you should do. Again, if someone came up to you with a bad idea and asked how to change something on it, wouldn't you tell them it was a bad idea and they shouldn't be doing it in the first place? I think so.
If you're wasting your time on a system like that, whatever. Have fun tracking down parts for hours, putting it together for some more time, and then realizing your final product still is unable to do anything to almost any degree of satisfaction. It's almost a joke you're selling the thing for real life use, and I feel bad for the uninformed buyer who takes part in your deal for a low cost system, when far better system can be purchased for the same price. There's almost nothing you can do with this system, in today's terms.
And, if you look at it, generally I did answer your question. Even if you found the parts, I'm about 90% sure that the unit couldn't handle the heat, and doesn't have the power for the new CPU. At any rate, they didn't even make Pentium II's for the mobile sector over 266MHz - and if you attempt to stick a desktop chip in, again, you'll run short in terms of power and cooling. The TDP increase from the mobile chip to the desktop version, BTW, is in some cases greater than 30W, and consistently greater than ~15W. Upgrading to the 266MHz (increase of a few watts only) version is about as worthless as this entire project together.
So, there. It's not that it can't be done, it's that it shouldn't be done. I'm done talking to you now. Notice how no one else bothered to give you any information at all - you'll be lucky for a glance from me in the future. There's no law saying I must answer your question or die (especially if it's just a silly idea), BTW. I gave my opinion, and now I'm done. Fret with your age old machine if you will, spend your time unwisely and sell it to some poor guy who doesn't know any better. Just won't be me.