On Nov 21, 12:05 pm, marcin.waligora
wrote:
Thanks for the reply.

I've tried that. Unfortunatelly, when I rename it to for example to .xslx I
get an error that the file is corrupted (because it's not .xslx). Do you have
any other ideas?

Sorry, as you've already figured out you can't just rename the
extension because it's proprietary to Office 2007. I can't find any
info on how to disable that specific warning, but you may find
something in the Trust Center in Excel 2007. In Excel 2007, go to the
Office button -- Excel Options -- Trust Center (on left) -- Trust
Center Settings. Perhaps within one of those categories is your
answer. I wish I could've been of more help.

Cory