For all of my Excel spreadsheets when I attempt to open them (by double-clicking in explorer) I get the message "Windows cannot find C:...". The files are there, and are valid zip files as seen by 7-Zip. There are no apparent lock files in the directories.

I did just install Norton-360 over the weekend (replacing Kasperski), but the Norton log shows no events related to Excel. However, while installing Norton I did reboot with some Excel files open.

Presumably something is hosed in my Excel configuration but I don't know what.

Update (Before actually posting) -- I found an article that suggested turning off Advanced Option "Ignore other applications that use DDE", then doing excel.exe /unregister followed by excel.exe /register. I tried this but I suspect that the two Excel calls were ignored (Excel opened, but no obvious change). With that option off the spreadsheets load OK, but not with it on. And, curiously, spreadsheets load OK with the option on or off if I open Excel first and then open the spreadsheet in it.

Does anyone have any idea what effect leaving that option off will have?

Update 2 -- I tried running the "repair" option. It said it corrected a couple of config things (without saying what they were), but I still get a failure if I double-click an Excel file with the "Ignore other applications..." option checked.

Update 3 -- I managed to fix this problem, but failed at the time to come back and say what I did, and now I can't remember for sure. But I think it had something to do with "Options"/"Save" and some of the values there. Something to do with AutoRecover, perhaps. (Possibly there was a file in recovery and I had to specify "Disable AutoRecover for this workbook" to let bring-up get past it. Or perhaps the AutoRecover file location was hosed.)

Anyway, if it happens to someone else, and you find the fix, post it below and I'll mark it answered.