Please help,i am trying to download from windows critical downloads,it seems that it come into my pc,but when i check the download site it tell me that i need the same critical download again,i have windows xp home edition.
The Windows Update scan engine can make mistakes. Sometimes an update has been properly installed but WU insists that you need it again. Sometimes after a while, it will stop.
You can also click Installation History on the left and scroll down to see whether the update has ever been successfully installed (you'll get a list of the recent failed attempts, but go through the entire list).
If you're really worried that it might not have been installed properly, you could go to Add/Remove programs, and see if it's listed there, then remove it. Restart, and let WU install it.
If in doubt, for every update listed after the scan, there's a "Read More" link, which takes you to the bulletin, which contains a further link to the download site for XP. Click the link and click Download on the page and choose Save to Disk. (This is a better way of keeping these updates .exe files anyway, if ever you need to reapply the updates.)
After saving it to disk, double click the .exe file and see if it will install.
You could also check yourself whether an update has been properly installed by going into the registry (using regedit), and then compare the file version number stated in the registry key with the version number of the actual file (which is supposed to have been updated) on your computer. Don't think you need to do that. If you're really interested, post back.