Dell Dimension 4600 Upgrade

I have a Dell Dimension 4600 with Windows XP Home Edition 2002 SP2. It currently has a Pentium 4 CPU 2.8GHz, and 256MB of RAM. I am looking to upgrade it to but don't know where to start. I am thinking about investing in RAM upgrades, but don't know what XP SP2 will recognize maximum or even if this is where I should start to get the biggest performance boost for my money. Any suggestions? And yes I know this probably isn't the most cost effective method of getting a more powerful computer but it is my best option.

OPowell16  

The Dimension 4600 will support up to 4gb [4 x 1gb modules] of DDR RAM, but may only address 3gb-+ of it due to the 32-bit operating system:

http://www.crucial.com/usa/en/compatible-upgrade-for/Dell/dimension-4600

Also, if you are using the 4600 for internet browsing, best to replace XP with a more current operating system eg Win 7.  

http://answers.microsoft.com/en-us/windows/forum/windows_7-windows_install/can-i-put-windows-7-on-a-dell-dimension-4600/ba4efe5f-d990-49b4-bff7-e43b6b133007?auth=1

You are no longer able to update Windows XP, more information about this, can be found Here:

https://www.theguardian.com/technology/askjack/2014/apr/11/how-can-i-use-windows-xp-safely-now-its-no-longer-supported

Bev.