There are currently 2 available options for system RAM with the Aspire One netbooks.
The first is 512 megs of RAM that comes with the 120Gig hard drive option,
The 2nd is the full 1 Gigabyte of RAM that comes with the 160Gig hard drive option.
Keep in mind that some of this is shared for video, but it's all DDR 533Mhz RAM, and You can add more to both systems later.
Your Choice. Hope this helps.!