new memory sticks

[nipdog001]

It has been a awhile since i messed with upgrading memory, I pulled out a pc 2100 ddr 128 133mhz, looking at upgrading to possibly 512 or 1 gb, but all of the listings are for pc 2100 are showing 266mhz, my question are these memory stick compatabile with the current system, the memory bus is only 133. from what i remember that they are, this guy lives out of state and i visted over weekend so did not get full system information he has hp 503w system, not that that helps much, sorry for the beginner question, i looked online before posting and most information was that 266 is compatiable, but i knew someone on here would be abl to give me the low down thanks for your answers !

[ski]

DDR stands for 'Double Data Rate', so DDR 2100 266 MHz is compatible with a 133 MHz memory bus.