Dell won't provide software support beyond asking you 5-10 questions that'll let them know for sure if it's hardware or software, and then if it's software telling you to use the system restore disc.
It's either a software problem or something that his wireless provider has changed or filtered.
1. Click start, then Run on the start menu. In the box that comes up, enter "cmd" and click OK.
2. in that window type "telnet www.google.com
80" and hit enter, and when the screen clears, type "get" and hit enter.
If you see output, something has gotten funkified in the way your browsers are seeing things. I'd recommend uninstalling firefox, reinstalling it and telling it NOT to import any settings from IE and see if that works.
If you don't see output, either your computer itself is filtering the connection or the ISP is. If your computer has additional firewall software, check to see if it's got anything to say in the list of allowed programs or connections, or try turning the firewall off, then try browsing with IE or firefox, then re-enable the firewall. If this doesn't work, it looks like everything is setup right, or you don't have additional firewall software to check, it's time to test at a wifi hotspot or call your ISP.
Since google earth can browse, and can browse to sites that aren't google earth, I'd say this is most likely NOT at the ISP, since any port filtering they'd put on would block everything that's web traffic. This is most likely going to be something with a firewall, or something that's infected your computer. If something's infected your computer that's doing things THIS odd, back up any useful data, and do a system restore, making sure to format your hard drive in the process. Malware doesn't tend to interfere that noticably with the operation of your system unless it's a pretty nasty one, and the nastier ones, despite anyone posturing and what not, are less work and have a better outcome if you just re-format and re-install instead of trying to clean them off, and whatever else might be there that the cleaner apps can't see.