Question : What is blocking user internet access?

I've been called in as a new IT person and I'm trying to figure out what the last IT person did.  It's a Server 2003 domain.  A verizon modem with a built in router , nothing fancy.  On the workstations, depending on what user is logged in, I can't access the internet.  For example, if I'm logged onto the domain as Administrator everything is ok.  If I log off and sign back on as Harry (still logging onto the domain) internet access is somehow restricted.  Where should I look to find this?  I know a couple ways to restrict computers but I'm drawing a blank on restricting users. Please help.  Thanks.

Answer : What is blocking user internet access?

What can't they do?  Can they resolve host names?  If you put a hosts IP  address of an external web server in the URL can get bring up a the page?

Does the output from "ipconfig /all" look right?

Does IE Network configuration look O.K?

Better yet, are they supposed to be able to access the Internet?

Is there a firewall?

What group(s) is Harry in?

What GPO's are applied to those groups?