Scanning can be intense. The scanner has to create cryptographic hashs of
the files that it tests to compare to a list of bad files.
Are you doing a full scan, or a quick scan? I would encourage you to do a
quick scan, and reserve a full scan for when something is found, or on some
less frequent scheduled basis.
When this happens to OneCare users (the same scanning engine in
Defender and OneCare) the problem is almost always caused by a
conflict with other software on the PC, typically security software
that provides real time protection/scanning. Basically, each file that
the engine touches to look at, the other protection software
intercepts to check, too, and a deadlock occurs.
-steve
