hey - has anyone ever run into this problem before? or know how to tackle this? i had 1GB on the mobo (2x512) and now wanted to upgrade to 2GB. there are only 2 slots, so I wanted to get rid of the older modules and just put 2 new 1 GB modules. my computer won't boot up with either of the new modules fixed in. with 1x512, it boots up. with 2x512 it boots up. with 1x512 & 1x1GB, it won't boot up. with 2x1GB also it won't boot up. the computer sometimes gives 2 beeps, and sometimes gives continuous long beeps forever. i looked up the beep codes and they said it had something to do with memory, but i don't know how to debug this situation. here's the mobo: nVIDIA® nForce3 250 http://www.ecs.com.tw/ECSWeb/Products/ProductsDetail.aspx?DetailID=502&MenuID=21&LanID=9 anandtech.com has decent reviews. the mobo site says it can handle 2x1GB; it's not dual channel. and the memory brand - here's the thing: i bought it on ebay and just got it today. from "fastmemoryman" (that's the user - who has over 3000 reviews and 98.5% positive). on the cover, i see www.emartbuy.com and on the memory stick, here's what i see (on a sticker) 1GB DDR PC-3200 400 Mhz Module DIMM the 512 module that works has the same exact info on its sticker (except it says 512MB instaed of 1GB). so, if anyone has ever run into this compatibility issue, please let me know. i gotta try something by wed and return this first thing thursday morning if it won't work out. thanks to anyone who responds.