Vista Works Spreadsheet search

I have Vista Home Premium and use forty plus Works 8.5 spreadsheets.
All spreadsheets are saved in a folder located on the local C drive.
I am unable to perform a search of the spreadsheet contents from an Explore
window. Using the same technique I can successfully search the contents of
Adobe documents. If I open the spreadsheets and use Works search I can find
the string that fails from an explore search. The search folder options I
have set are:
Always search file names and contents; Include subfolders; Include partial
matches; Include system directories; Include compressed files.