When Pocket PC connected to Windows' ActiveSync, it not only able to sync data with Outlook, but also able to connect to Internet via the PC being connected to. However, I got an error "The page you are looking for connect be found due to unknown error. 0x80072f78". This problem has prevent me to update my Avantgo.
Since my router at home has broken down for unknown reason, I cannot get my Acer n300 connect to Internet. So, I made a rough search online and found the following pages:
Activesync 4.2 now available for download from Jason Langridge's WebLog - MR Mobile!
ActiveSync 4.5 and Weatherpanel problem from Aximsite.
Both pages has point out that the error is due to new ActiveSync has "a problem with Desktop Pass-through ... caused by a Layered Service Provider (LSP) that use the Windows TCP/IP stack." This known issue can be solved by enabled the LSP by modifying the registry manually. This solution has absolutely *no* warranty and use at your own risk!
Open the registry (run RegEdit), locate: HKEY_LOCAL_MACHINE\ SOFTWARE\ Microsoft\ Windows CE Services\, and add "AllowLSP"=dword:0. Restart your ActiveSync. You may kill the process using Task Manager, and restart from Start menu. Alternatively, you can reboot your computer (of course).
This work for my Acer n300 and ActiveSync 4.2, on Window XP Pro (English).