in its place. Test it thoroughly. If you get it working properly ...then add the old RAM in the remaining slots. Make sure you put the matching DIMMs in the designated DIMM slots...it should boot up and say something like 128bit or dual channel RAM
Make sure you disconnect the PC from AC power. . . . there's still power to the MB when it's plugged in and not running.
Let us know.
I have a Gateway FX400X Desktop XP Windows. I have 1024 MB 533 MHZ Dual channel DDR2 SDRAM (2-512 MB modules). I have left the original RAM in and have installed 2-1 GB DDR2 PC2-5300 667 MHz to upgrade RAM. Is that okay to leave the original RAM in? When I go to control panel/system, it still shows 1024 MB RAM. Shouldn't it be showing 3 GB RAM? or does that ever change?