I got a message under Tune up saying that an unknown error prevented disk defragmentation from being executed. I tried using my system tools to defragment and that will not work either.
You can check a few things. You need about 15% free disc space to successfully defragment a hard drive. Check t see that you have sufficient disc space available. You also might try running a check disc. Disc errors will cause defragmentation to fail. If you have sufficient free space and running chkdsk does not resolve the issue please contact support. How to reach support - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2