If any file can not be deleted, then you can use the program LockHunter, which removes the active connections of other applications to that file, which allow you to change or delete file.
In this day of age, it's very practical to have a Windows 7 installation on your USB key, for many netbooks and devices don't come with CD/DVD drives anymore.
When you want to copy the result of the cell to another cell in Excel, the target displays an invalid references error messag. This error can be avoided by copying cell value into target cell and not the whole formulas.