Toshiba RAM upgrade not recognized

I have an older model Toshiba Laptop Satellite 2805-S603 it is upgradeable to 384 by changing the RAM chip to 256 PC 100 -- now the first chip I purchased didn't work at all so I exchanged it for another (cheaper :) ) but when I check the status it still only shows the original 256 RAM...? I also have had to reformat the HDD and reinstall the OS runing windows XP home -- now waiting to see if it will recognize the upgraded ram.. any pointers out there that may be causing the problem?

so it has 256, and your trying to add another 256 to get to 384?

not going to work bro, its out of physical address, cant reconize that chip in that slot, the density is to high/or miss matched.

does it work with just that upgrade module or did toshiba in their wisdome hardware in the original peice?