My computer is way slow and i don't know much of Technology what can i do?

i just bought a used computer and it is really slow i have a high speed internet i don't know much about computers so i don't really know what to do people had told me that i can buy rams or something like that computer specifications are intel Celeron 2.4 ghz, 400 mhz FSB (100MHz4) chipset:845 gv memory: 256mb pc-2700 ddr hard drive: seagate barracuda 40gb ata/100 7200 rpm and i don't know what all this mean it just said in the ad when i bought it well are these numbers not to bad for my computer to be slow i mean slow taking about 5 min. or more to load a page can i do something about it also there is some icons that says:window live one care (status fair) or sometimes it says (status at risk) what does it mean? or what can i do to fix it do i have to buy something or can i fix it by my self thank you