This update keeps coming up on Windows update and installs. Every time I run Windows update it shows that KB915597 is available for download.

Hi Javier This is by design. Windows Defenderwill appear often in Windows Update. It is constantly updated with informationabout the latest spyware and other threats to Windows that are discoveredon an ongoing basis.All of the Windows Defender updates will have that same (KB915597) number.See this article for more information.Description of Windows Defender definition updatesHope this helps. Ronnie Vernon MVP

Newer definitions for Windows Defender come out at least twice a week. To see if the latest ones installed, click the Start orb, in the 'Search programs and files' line type in defe, now click on Windows Defender.At the bottom of it's window you'll see 'Antispyware definitions:'.The Version number and the date created along with the time will now be showing.As of 2/5, the Version should now be at 1.51.303.0. It was created on 2/5/2009 @ 2:30 AM.Is that what you're seeing, Javier ? MowGreen MVP Data Center Management - Update Services Consumer Security