What would make this workbook non-searchable?

Howdy -

I'm working with a plant ecology dataset The fields under the column "% foliar cover" are populated with P's, signifying "presence." I want to substitute 0.5 for P.

Only problem is, find and replace doesn't work. I suspect there's some sort of weird formatting thing going on. I can edit it by hand, but there's several hundred P's to replace, and doing by hand is not an option. Does anybody have any general ideas what this might be?

Maybe there's a trailing space or a non-printing character. Use the LEN function -- it will be 1 if the cell contains a single character.

How would I do that in Excel '07?

It hasn't changed: =LEN(A1)

Didn't quite work. Hmmmmm.

What didn't work?