I want to upgrade my computer it's a dell dimension 2350. it has only 256 SDRAM but i want to either buy a another 256 SDRAM card or a 512 SDRAM card. what i have trouble with is when i see those different notches at the bottom of the card. do the different ways they look matter? (it's the side you insert into the port) and also does it matter what brand or kind besides it being SDR or DDR? also how can i tell what kind of RAM should i get? where will it tell me what kind of ram is compatible with my mother board. THANKS

SDR-SDRAM has 168-pins, DDR-SDRAM has 184-pins. They're notched differently too. SDR has two notches along the pin edge...one notch is about 1" from one end, the other notch is in the middle. DDR only has one notch that's slightly off center.

If your board uses SDR-SDRAM, you could run into density issues. All new RAM is high density using 256Mbit technology...older RAM uses low density 128Mbit technology. If your motherboard was built with low density RAM in mind, high density RAM won't work. Generally, if your board can't accept 512MB per slot, it can't use high density RAM.

http://www.kingston.com/tools/umg/umg04.asp

You could try going to Crucial.com & entering all the necessary info about your system

ASUS A7N8X-X
Athlon XP 1800+
8.5 x 200MHz
1280MB PC3200 2.5-3-3-7
Asus A9550GE/TD 128MB
WinME/WinXP Pro SP1