|Sorry about that, first-timer here :S|
Ok, I installed from installation discs (ones specifically for Dell systems). Deleted all partitions before I began. We are using McAfee VirusScan 8.7i which does not detect anything. I've also tried MalwareBytes, SuperAntiSpyware, and StopZilla to get rid of this problem. None have completely worked. The closest I came was with StopZilla which at least allows me to block the change to the homepage. SuperAntiSpyware will alert me that my homepage is being changed with an option to block it, but even if I tell it to block the change it still changes.
We've also tried to block all traffic from that site at the firewall level but even though users can't get to the page, the change to the homepage still occurs.
I will install winpatrol and see if I can see anything unusual there. Problem is I don't know what to block as far as files go at the moment.