Help, sporadic internet access

I apologize in advance for the length of this post...
I've been battling spyware & hijackers. I cleared lots of
spyware from my home computer (Home XP) over the weekend
using spybot & semantec. Thereafter, I could access the
internet, the other users (really angry daughters) would
get "file not found" when using both IE and Netscape.

So, I did a system restore to last Friday. We all had
internet access, but all the bad stuff was back on the
machine. So, I undid the system restore and then no one
had internet access. All I would see was file not
found.

So, I spent an hour on the phone with our DSL tech
support. They had me enter a static IP address, which got
me internet access, but still file not found for all other
users. I downloaded ad aware and hyjack this and ran them
both. But, same problem.

So, tech support recommended a reinstall of the OS. I
reinstalled last night and... same problem: no internet
access for anyone. When I entered the static IP address,
I had internet, but no other users do.

Any suggestions?? My daughters are threatening my life if
they don't get internet access soon!