Drivers issues. When you reformat, you wiped everything off the HDD - including the drivers files that tell the parts what they are and how to work. Retail XP disks only have generic drivers that give basic functionality (CD-Rom driver, Display, USB, etc.). Everything else would be specific to the system. It seems you're missing a few more, too.
What kind of computer is it? If big-brand, did you receive a recovery CD? --if so, it should have all the necessary files you need. If self-built, all the drivers will be on the CD that came with your Motherboard. Windows Update might take care of it, or just click on Update Driver.