Thanks. I turned off and turned on the system restore, and the scanned files decreased from several thousand files to about 40 files. The infected files could not be found, which is good.

There were also more than 2000 files that could not be scanned , mostly under \Windows directory. Since avast does not support ME, I am wondering if there is any work around to get them scanned by avast. I suspect that my PC is still infected due to various errors constantly appearing at different times.