Max RAM for Dimension 2400 Series

Hello. I have an old desktop computer I guess, it's a Dimension 2400 series, I bought it off a friend yesterday. At the moment it has 256MB RAM running on Windows XP Professional Service Pack 3 with Intel Pentium 4 2.80GHz. I have checked the system scanner at crucial.com and it states that the maximum RAM upgrade is only 2GB using DDR PC2700 or DDR PC3200 with 2 RAM slots. Could someone please confirm that this is correct or could I somehow run atleast another GB of RAM? The desktop is very slow and I can't see 2 GB of RAM improving the speed greatly. I use the desktop for various things at once and can't afford to buy a new one yet. Also, the BIOS version is Phoenix ROM BIOS PLUS Version 1.10 A05, if someone could provide me with a link to update the BIOS it would be much appreciated, I don't want to trust myself and end up failing the update and breaking the desktop, thanks a lot!