Vista Internet problems

[Pelo]

My girlfriends laptop has never-ending problems. The ONLY programs that can connect to the internet are IE7 and windows update. No other programs will connect to the net. Not firefox, iTunes, Messenger, utorrent, Visual Studio, AVG - nothing.

I have tried multiple firewall configurations. Zonealarm stops the net from working entirely. Windows firewall makes no difference on or off.

I have also turned off windows update because every time an update has been installed in the past, the whole internet dies again, killing IE7.
SP1 fails to install, it gets to 99% and reboots with an error message.

This has had my head banging on the wall for a while now. I don't want to put xp on it, but the machine has no vista cd or an on-boot system reinstall function. Of course I don't want to pay someone to fix it either

Any ideas?

Specs:
Acer Aspire 5100 18 months old
AMD Turion64 2ghz
1gb ram
vista home premium
broadband adsl

[Pelo]

It doesn't really need more ram, runs fine after I turned off Aero, indexing, uac, sidebar, defender, nortons, a multitude of background services, and reduced the graphics memory

Strangely when I installed zonealarm, the windows firewall advanced settings reported that THREE firewalls were running - Nortons Personal Firewall, Zonealarm and Windows - This despite Nortons being uninstalled and WinFW turned off.

I think possibly Nortons is funking with everything. It is the OEM Norton internet security 2007, are there any common bugs in this? I had a lot of problems trying to uninstall this program in the first place...