cannot double click on an excel file to open it

Try right clicking on an Excel file in Windows explorer or my computer. Click 'open with' (not 'open'); click choose program; in the box that opens, highlight Excel by clicking on it, check the box 'always use the selected program to open this type of file', click OK. That should reset the file associations for your Excel files.

What version of Excel do you have and what version of Excel were the files saved as?

If you open the files manually in Excel and then save or save as, does that restore the double click action?

Do the files contain links to other worksheets or macros that are stored in a different relative path on your PC than they were on the PC used to create the files? Any idea what libraries the message might be referring to?

One more thing to try, is to set the association manually;

Folder options, file types tab; when the waving torch has finished scroll down to xls., click on it to highlight it, click advanced; click on open to highlight it; open should be in bold, if not click on set default. Click on edit, check that the entries are as follows:

Action: &Open

Application used to perform action: "C:\Program Files\Microsoft Office\Office10\EXCEL.EXE" /e

[this assumes that you have Office XP installed (aka Office10) at the path indicated; otherwise substitute the correct path to your Excel.exe; remember to include the " " around the path.]

Use DDE box: checked

DDE message: [open("%1")]    including [ ]

Application: Excel

DDE Application not running: leave blank

Topic: system

Click OK, OK, Apply (if you made changes), close.