That board has a maximum FSB of 266? That sucks =/ But yes a mobile chip will work in there because for one, that mobile chip I believe has an FSB of 266 anyway so you really wouldn't have to worry either way, but if I'm mistaken and it's actually 333FSB, then it'd still work provided your motherboards BIOS has enough options in there that would allow for overclocking. You don't want to overclock, but you need some of the options that you use in overclocking such as the FSB otherwise known as the CPU Frequency sometimes in the BIOS and the multiplier. A stock 2600+ is like 133x15 = 2GHz that 133 is the CPU Frequency or FSB which when multiplied by 2 133x2 = 266 so that's how you get your FSB. It's due to the RAM being DDR which means DOUBLE data rate that you multiply that number by 2.
So if it's a 266FSB cpu then you have nothing to worry about. If it's a 333FSB CPU then you need to be able to adjust the FSB and the multiplier. So if it's 333FSB and your board only accepts 266FSB then you'd lower the CPU Frequency from 166 (166x2 = 333) down to 133 but then you'd raise up the multiplier so that you could still have the same clockspeed of 2GHz or whatever it's stock is.
Adjusting the CPU FSB also generally requires being able to adjust the AGP and PCI frequencies. The AGP needs to be locked at 66MHz and that'll automatically lock the PCI at 33Mhz where it needs to be.