I am using VB.NET to open and read info from Excel spreadsheets using code
similar to this:

Dim xlApp As Excel.Application
Dim xlBook As Excel.Workbook
Dim xlBooks As Excel.Workbooks
Dim xlSheets As Excel.Sheets
Dim xlSheet As Excel.Worksheet

xlApp = New Excel.Application
xlBook = xlBooks.Open(strPath & "SheetList.xls", True)
xlBooks = xlApp.Workbooks etc.

This used to work just fine, until I was trying to get similar code running
through ASP.NET, and was fiddling with permissions trying to get that to
work. Having given up on that, I now find that the VB.NET app, which runs
locally, is failing with an "access denied" error, which happens when it
tries to create the Excel object (xlApp = New Excel.Application). So clearly
I have screwed up access permissions. I could use some help un-screwing
this. I have already tried uninstalling and reinstalling the app and the
whole Office suite, I have tried clearing out anything in the registry that
might apply, and I have re-set Windows permissions in the folders this stuff
is in.