My computer is connected to the internet through an ADSL model. Every time I install a Windows Update and reboot, my ADSL modem refuses to work and I am unable to connect to the internet. The only workaround for this issue is to disconnect the modem from the power source and USB, then use System Restore to restore the PC to a point before the update was installed. Then, after the PC has restarted, reconnect the ADSL modem. How can I stop this problem from occurring? The computer is running Windows XP Professional SP2.

From the description of this issue, it appears Windows Update may be installing an update which causes the ADSL modem to no longer work correctly. When you do a System Restore, this is rolling-back your PC to a point before the update was applied (i.e. essentially uninstalling the update) allowing your modem to work correctly. If you regularly run Windows Update, and then always need to use System Restore to roll-back the computer after the update has been applied, there is no point in running Windows Update in the first place since you are undoing the updates which were applied. Without knowing exactly why the modem is not working (e.g. error messages) it will be difficult to diagnose and fix the issue. However, there are still some procedures to try. Firstly, try reinstalling the modem. Once you have run Windows Update and the updates have been applied, restart the computer and you will likely find the modem does not work. Now, uninstall the modem drivers and any associated software. Then, follow the original setup instructions (e.g. which were provided by your ISP) to reinstall the modem and setup your internet connection. By reinstalling the modem from scratch, you should be able to fix anything which was broken during the update process.

If reinstalling the modem does not fix the issue, the next procedure is to visit the manufacturer’s website and download any available updated drivers for the modem. Should an update be causing the modem not to work correctly, the manufacturer may have released an update to fix the issue. Finally, should all else fail, you should contact your ISP for support. Assuming your ISP supplied the modem, it may be their responsibility to help you reinstall the modem when you are unable to do so following the instructions they have provided.