Why does my computer fail to recognize ports?

Hello,
In a desperate attempt to fix my Acer Aspire 5710G laptop, I had installed Windows XP Service Pack2 on it. Before installing I had formatted all my Hard disk drives. Now ever since i installed it, I find that many of my ports are not recognized by my laptop. For example, i try to play music on Windows Media Player and i get this message that "the sound card is not installed properly". I also cant connect to the Internet using a cable as my cable port isnt recognized. What can I do? Is there any way i can fix it myself without having to give it to the technician?
P.S. my laptop has crashed before, and i have even installed Windows Vista SP2 on it, but i've never faced such a problem at that time.