Microsoft Security Essentials Exclusion List
Microsoft Security Essentials (MSE) Anti-virus program has received a lot of good press since it was released in Sept 2009. I have been gradually moving my residential customers, friends and family over to it. One small problem I have noticed: at times the MSE engine will hog up quite a bit of cpu cycles. I recently found a blog post that said that adding the MSE folders to the list of files/folders in MSE to be excluded from scannng will help reduce the high CPU usage.
To add exclusions, click on Settings > Excluded files & locations, then click the Add button to add an entry.
For Windows XP, add the following exclusion:
C:\Program Files\Microsoft Security Essentials
For Vista/Windows 7, add the following exclusions:
C:\Program Files\Microsoft Security Essentials
C:\Program Data\Microsoft\Microsoft Security Essentials
C:\Program Data\Microsoft\Microsoft Antimalware
Hope this helps. Let me know if there are other folders/directories that should be excluded