You'll have to see if Daewoo has a website with a bios upgrade for your mobo to run a 133 fsb cpu. Otherwise, the 800 (with 100 fsb) may be the fastest cpu you can run. The slot 1 cpus cost more, so you may be better off getting a new mobo combo with cpu, or a "pc kit" with mobo, cpu/heatsink, and case. Pricewatch has pc kit listings for almost any cpu. Then, all you have to do is transfer your hardrive, video card, cd, etc to the new case. You'll also have to do a fresh install of windows with the new mobo. The athlon combos are pretty cheap, but you'll need a new power supply anyway to support them if you use your old case.
If your board supports ANY coppermine (Celeron 566 and up, PIII 650 and up, are all Coppermine), it will support the common PIII 850, and should also support the hard to find PIII 900, 1000E (the 100MHz version), and fast Celerons (up to 1.1GHz, much less powerfull than PIII's).