Why does 128 MB of 100 MHZ SDRAM cost more than PC 133 ram of the same size? I have 128 SDRAM in my HP Pavilion w/ 750 Athalon, and want to add another 128 mb stick. I can't find one for under $30, even on Ebay! Yet PC 133 is only like $12 on ebay (I know, my friend bought some). I have to use either 66 mhz or 100 mhz in my system. I want to add more memory since I'm installing Win XP as well. Computer manufacturers suck, my friend can't even use the memory he bought because he has a compaq and you have to use THEIR memory!