well, that link showed what processors the motherboard support, the maximum amount of memory, and what type of graphics card and stuff, but you didn't list your specific parts you have in your build. regardless, the single core pentium (regardless of which one you have) is the best processor you can put in it. Whatever amount of RAM you have, 1GB is the max, so I would make sure you are at least using 1GB to help it run the best it can. And whatever graphics card you have (if any...you may only be using integrated graphics) just get the best AGP card the motherboard will allow......that's the best your going to do with that system...doing all that will make it ok for internet and typical stuff, but not gaming. you may want to put any upgrade money at this point towards a new system. i would recommend a dual core processor system with a decent PCI-e graphics card and 2GB of ram.
Antec 300 Case, Intel Core 2 Quad Q9650 @ 3GHz, Gigabyte GA-EP43-UD3L, PNY 4GB PC6400 800MHz DDR2 RAM, XFX Radeon HD 5550 1GB DDR3 Ram, 1TB Western Digital Black 7200 32MB cache, 64-bit Windows 7 Ultimate SP1, Antec Earthwatts 500 Watts