r yakulis

I use microsoft xp professional and we have 5 user areas.
One two of the user areas, they cannot access the internet
because there is an address in the web window which is a
non-functioning address. Whenever I try to delete that
address, and put in a new address, the computer reverts to
the previous address and the two user areas therfore
cannot access the internet. The other user areas work
fine. I ran a viral scan online from Norton's, with my
own software, and a third party (our computer tech people
where I work) and all scans for viruses are negative.
Help!
Bob