Losing internet connection on Windows XP

Hello,
I have a Sony VAIO desktop, 5 years old running windows XP. Recently, I started getting ntoskrnl32 missing and refused to boot. My local computer guy said that it is a hard disk problem and ended up putting new hard disks and reinstalled XP. But I keep internet connection after about 5-10 minutes. If I disable and enable "Local Area Connection" it works for sometime and stops again. Could someone tell me how to solve the problem? I have a Cisco wireless router that I use. I use that to browse with my iPhone as well.

Thanks a lot in advance,
Sid