See KB Article for a fix.

http://support.microsoft.com/kb/941636/en-us


Gord Dibben MS Excel MVP

On Fri, 23 May 2008 16:48:00 -0700, jr wrote:

I often receive Lotus 123 files and have opened them with Excel without
problem. I just downloaded Service pack 3 for XP and now am unable to open
them with Excel. I receive a message "you are trying open a file blocked by
your registry policy setting" What do i do??