DSL connection to the Internet, Windows 2000, IE6. Logged on to my ISP, can browse the internet through IE just fine. However, any time I try to download an update to IE (the stub installer gets dropped down fine but part 2 of the insall doesn't happen because the installer can't find the Windows site), download a Windows service pack update through the Windows site, or register any non-Windows software (ie Zone Alarm won't install unless you register it first, ugh), I get a message that varies with each software, but basically says that 'no connection to the internet is available'. I assume these programs are looking to my IE connection settings to determine how they should get out to their destination IP/site, and the settings are correct. No proxy server, no site blocking enabled anywhere, no firewall. But no programs can find the internet besides the browser. I'm stumped - and I'm so tired of troubleshooting this one. Any ideas?

Go into Internet Settings (right-click IE on your desktop), select Properties, then tab Connections. Select the current/default connection, then click Settings...
On the bottom left is a box -Do not allow Internet programs to use these settings-
Make sure that box is cleared. If it was not, that was your problem.