X97M/Clonar is a simple Excel 97 macro virus.
Disinfection & Removal
When an infected workbook is opened, X97M/Clonar.A disables both "Tools/Macros/Macro" and "Tools/Macros/Visual Basic Editor" menus.
Then the virus creates an temporary file, "C:\Windows\Diablos.bas", and it uses this file to infect all open workbooks.
Every 30th day of each month the virus activates its payload. At this time X97M/Clonar.A changes the size of toolbar buttons to large.
Technical Details: Sami Rautiainen, F-Secure