Problem
When you are installing Microsoft Security Essentials it stalls with the message “Installing Security Essentials…” and may never progress.
Cause
The installer may be stored in a folder with limited permissions.
Solution
When you download the installer, save the file to your Desktop.
If using Internet Explorer, make sure to choose the “Save” option instead of “Run”.
Was trying unsuccessfully to install on vista on older computer without success. Your suggestion worked like magic! Thank you!