Webuser Forums: Web pages won't load

I bought a new PC less than a month ago - emachines 4252 from Currys. The specs were good and just what the family needed after our reliable but slow 1999 Time machine.
For two days everything was fine, the only niggle being a problem with the PC communicating with the printer, which we figured we'd be able to sort out online eventually.
The internet was great for those two days, until one Tuesday lunchtime when all of a sudden web pages would not load. This was the case in both Firefox and IE7. But curiously there was a connection to the internet.
I also cannot access my Thunderbird email account, but can get onto the iTunes store, which confirms there is an internet connection.
I have uninstalled and re-installed the modem software - Speedtouch 330 - on a few occasions, and done likewise with updated drivers, following advice from threads on this forum.
The OS is Vista Home Premium and my ISP is Orange. The Orange tech support asked for a lot of information before linking me to various articles on its help and support pages, which weren't very helpful or supportive.
I should also add that my son has no problems using broadband on his laptop using the same modem and connections. That's how I'm writing this at the moment.
Any help will be greatly appreciated.

Post Extras