I can't access the internet

I can't access the internet from my desktop after installing sata Seagate Barracuda 500gb hard drive. (The motherboard is three years old and ran a 200GB ata drive before.) I installed Windows XP and service pack 2. AT&T, my ISP, says that a driver for the ethernet isn't enabled? I am able to access the net through my wireless laptop, tho. I am not all that savvy so am hoping for some step by step help. The hard drive was OEM so no manual or anything. I had no trouble with the cables for the install, after I bought them.