Change the Number of Undo Levels in Excel 2000 (All Versions)
This tweak lets you modify the amount of undo history information that Excel will track. Increasing this value allows you to undo more than the default number of changes.
Open your registry and find the key below.

Create a new DWORD value, or modify the existing value called 'UndoHistory' using the settings below.

Exit your registry, you may need to restart or log out of Windows for the change to take effect.






(Default) REG_SZ (value not set)
UndoHistory REG_DWORD 0x00000064 (100)

HKEY_CURRENT_USERSoftwareMicrosoftOffice9.0ExcelOptions



Settings:
Key: [HKEY_CURRENT_USERSoftwareMicrosoftOffice9.0ExcelOptions]
Name: UndoHistory
Type: REG_DWORD (DWORD Value)
Value: Number of Undo Levels


Disclaimer: Modifying the registry can cause
serious problems that may require you to
reinstall your operating system. We cannot guarantee that problems resulting from modifications to the registry can be solved. Use the information provided at your own risk.


Last Modified: February 27, 2001



Credit:

http://www.winguides.com/registry/