I only have usb ports and my keyboard doesn't work during boot

I have a Dell Dimensions e521. I cannot go to Bios to change settings because my keyboard doesn't work until windows xp starts. I don't have an outlet for a ps/2 keyboard. I can't go to safe mode, or any other option that I have to chose from before windows xp starts because my keyboard is not recognized. Is there a way that I can fix the situation? Dell sucks!!!!! Why would they build a computer with only usb? I have never seen or heard of anything like this.