The next part depends on your motherboard, if you look up the supported RAM in the manual it will tell you all the supported chips. if you are totally replacing the RAM then you can grab whatever from that list. if you are adding to your existing stuff it gets a bit more complicated, any ddr2 should work but you will end up running at whichever frequency is the lowest.
In short anything will work, or at least it should. but a bit more detail on your setup and if you are upgrading or fully replacing the ram will help.
Good news in the RAM looks cheap as hell, well I suppose that makes sense because its ancient...
How much you looking to add? I cant find a spec sheet for that motherboard so that makes it a bit tricky, how many sticks do you currently have installed, does that board only have 2 slots? (that's all I can see on pictures from google)
You don't want to go busting out 2Gb DIMMs if your motherboard doesn't support it, how much you looking to add, how many do you currently have installed and what capacity are they?
Well any ddr2 will do, so long as the capacity or frequency is outside the boards working range.
I don't think size will be an issue because you will only be adding a 1GB DIMM anyway. 266Mhz is actually 533Mhz (because ddr is double data rate) and speccy reports it without doubling it up. So you are looking for 533Mhz DIMMS at 1GB capacity.