Explorer 6

We are currently using Dell Power edge server, Trovit, win 2003 server and over 40 clients. Our clients use xp pro. I have a problem with explorer 6. The problem keeps on re-appearing every time. I always have to set the proxy settings in internet explorer(Internet options), the IP add and Port in adv settings because the client cant access the internet. This problem keeps on reccuring everytime and I cant seem to find out the problem!! Please heal