What to do if the update application reports that a filesize mismatches?

If you received a warning such as:

You should stop the installer, and clean up your temporary files.
To do that, click on START-PROGRAMS-ACCESSORIES-System Tools-Clean Up

This will clean up temporary and unused files in your HD.

If you're an advanced user just open a cmd prompt window and type:
    del %temp%\EZ*.bin