Microsoft always certificate their updates and ensure they are virus free, so they are safe to download via the Update page for your software version. Whilst other sites may offer downloads directly, the action of installation from a non-MS site will not update your history installation file (MS read this when deciding on updates you require when connected to update page). I run XP Home and all critical updates have been installed with no problems. It is worthwhile considering backup software to make an image of your C Drive in the event of a bad system crash. This way, you can restore your system (that you have regularly updated!) without having to reinstall the basic OS and update everything again. I recommend (and use) Norton Ghost 2003.
Randolph Carter, August 2003