Problems with usb and monitor

Hello,

I got my computer a few months ago and everything worked fine. Problems started when I hooked up my printer a couple of weeks later. I turned on my computer and after the xp logo when it goes blank for a few seconds, the screen never apeared. I noticed that my printer was on though, so I shut off the printer and restarted my computer and everything was fine. The printer works too, I just cant have it on when I start up. So I figured it was my printer. Yesterday, my card reader for sd cards and usb 2.0 never did work so I called the person who built my computer and the wire that plugs into the usb on the board wasnt connected. So I connected that and everything worked fine, untill today when I started my computer, it did the same thing as what the printer did when I left it on. Im waiting to hear from the person who bulit the computer, but I just wanted to hear what you guys think.