MonitorWare Knowledge Base

help!! i had my computer givin to me for x-mas. it is not a factory computer. it was custom built. i am not a computer wizard. i have downloaded so much stuff, tried to do stuff i think your not supposed to do unless you have a brain, and just thourouly screwed my puter up.
How do i copletley wipe my system clean? can i do it without the xp disc?
can i do it without a working floppy?
please help.