I wasn't able to come with an answer regarding sr.sys.
One last thing to check - right-click on My Computer, Properties, System Restore.
Make sure you don't have system restore disabled on the C drive.
Also - check the settings for SR, have you allowed Windows enough space for SR?
Is your hard drive getting full? If there's not enough disk space, SR cannot work.
Do you need to have a disk cleanup? The simplest temp file tool is ATF cleaner, it will remove files safely and clear disk space for you. Doesn't need to be installed.
http://www.snapfiles.com/get/atfcleaner.html