A. You can change the number of undo levels in Excel to any value from 0 to 100. The higher the number, the more resources the software will use to remember the previous states. To configure the number of undo levels, perform the following steps:

  1. Start a registry editor (e.g., regedit.exe).
  2. Navigate to the HKEY_CURRENT_USER\Software\Microsoft\Office\10.0\Excel\Options registry subkey for Excel 2002, or navigate to the HKEY_CURRENT_USER\Software\Microsoft\Office\9.0\Excel\Options registry subkey for Excel 2000.
  3. From the Edit menu, select New, DWORD Value.
  4. Enter the name UndoHistory, then press Enter.
  5. Double-click the new value, set it to a value from 0 to 100, then click OK.
  6. Close the registry editor.