Just windows going bad... 9x and ME did that all the time. Either reinstall windows, or upgrade. Has nothing to do with Internet Explorer, other than it may be triggering Explorer.exe to crash.
Manually extracting files to the system directory is a bad idea, unless you really know what your doing. Chances are they've been patched by a hotfix or service pack somewhere along the line, and replacing it with an original version would do more harm.