Default number formatting

Hi,

I am currently experiencing some difficulties with my number
formatting within Excel 2007. I have a fairly complex series of
worksheets, which now seem to be defaulting to the Accounting format.

I think that I may have done this through a replace all, somehow
setting the cells to all be Accounting format. Peculiarly when I add
a new worksheet, the cells also default to Accounting format

Is there a simple way in which I can use a combination of Replace all
and formatting to reset all the blank cells to be to be in General
format?

Many thanks,

Ben