i got a 4600 dell dimension

2.4ghz and 800mhz fsb
256 ram 400mhz

i read this article
http://www.epinions.com/content_108956585604

and he/she say that i buy 2 sticks of 256mb from dell and return to dell the ones that came with my computer which i didnt really understand how its cheaper..also..or should i just buy a 512mb stick and add it to whatever i have which is(2x128 i think) 256mb i thought we werent suppose to mix like 256 and 512mb together so i dont know how it really works...should i do what that guy say or buy the crucial memory and is it good to have a 512 and 256..if i am wrong about the specs of my pc please tell me that would really help

I'm just answering your questions about the RAM. As for the returning the RAM and getting new. That is your decision. Now.... Getting top of the line memory (Exp: Crucial Memory) isn't what you need unless your plan to overclock your computer. That isn't going to be likely because you are running a Dell, and the BIOS options are probally locked. Moving on..... If you do plan to buy more ram you will want to buy:

PC3200/DDR400 - Because the speed that is allowed on your computer is DDR400, so why clog it with slower memory.

2 sticks of RAM - If you want 256MB of RAM in your system buy 2 x 128MB sticks, or if you want 512MB of RAM in your system buy 2 x 256MB of RAM. This is because your computer runs in Dual Channel mode. This is so that your 800MHz FSB on your CPU will be equal to your FSB on your memory 2xDDR400=DDR800.

Recommend buying -
256MB Kit - http://www.newegg.com/app/ViewProduct.asp?description=20-141-421

512MB Kit- http://www.newegg.com/app/ViewProduct.asp?description=20-141-422

Also when after installing the memory make shure you get into the BIOS (Belive it either hitting the "Delete" key while the computer is booting up, or hitting the "F10" key while booting up) if you don't know how the Dell website will tell you how to. After getting into the BIOS make shure you enable Hyperthreading and Dual Channel DDR. I promise they will be in there.

Good Luck.