Multiple Programs – M.DLL
Most commonly, a browser helper object called m.dll installs with a new variant of the SearchAssistant adware program. This program resets your home and search pages to a blank page (about:blank). It may also generate popup ads. To remove this file, click on your "Active Tasks". Kill the file there. Then go to your "IE Helpers" Tab and remove the file there.
Less commonly, m.dll installs with Macro Magic by Iolo Technologies at http://www.iolo.com. This program lets you create macros for repetitive tasks.
Safe if not Adware
iolo