Today I manually update virus defination from Microsoft Security Essentials Update Tab. I can see MSE Update notifies that the virus defination is downloaded then switch to Installation. At this moment the green bar is near complete but it just hang indefinite with the message "Installing..." Please help.

After checking the issue, it seems this is a general MSE related issue. As this forum focuses on Windows 7 security specific issues, this inquiry would best be posted to MSE forum: http://social.answers.microsoft.com/Forums/en-US/category/mseThe reason why we recommend posting appropriately is you will get the most qualified pool of respondents, and other partners who read the forums regularly can either share their knowledge or learn from your interaction with us. Thank you for your understanding. Also, for your information, I'd like to include the following article regarding the issue: Why aren't virus and spyware definitions getting updatedhttp://www.microsoft.com/Security_Essentials/HelpTopic.aspx?mkt=en-us&assetId=e34036a7-7e21-4a69-8ae7-8ab2d3953e32#mainNavSean Zhu - MSFT

I have also problem with updating Microsoft Security Essentials. Uptate was automatic and after pressing the shut down updating started. After 10 hours saying: update 1 of 1 I had to foce a shut down. Very soon after start and login the system hangs. Finaly I managed to reset the system a few days back and tried to uninstall MSE but with no luck. I found a Fixit program that helped me and after that made an update of MSE. Now it works. (To find this took me about 8 hour of my life). Today I tried to update another computer and it also hangs the same way. I used Microsoft update this time. On both these computers the MSE were installed and have worked with no problem. However I noticed that the icon a tent with a flag was not seen on the lower right corner or on the program list. Operating system Windows XP. The computers are only used for bookkeeping. What have happend?