Question : Can't choose program to open a file

I right-click on a file in Explorer and select Open with... and then Choose program... Before I can select or browse for a program, the file opens in Textpad!  What to do?

Answer : Can't choose program to open a file

Click Start, Run and type Regedit.exe (press Enter)
Navigate to the following location:
HKEY_CLASSES_ROOT \ Unknown \ shell
Backup the key by exporting to a REG file.
In the right-pane, double-click (default) and type openas as its data.
Then navigate to the following branch:
HKEY_CLASSES_ROOT \ Unknown \ shell \ openas \ command
In the right-pane, double-click (default) and set its data as follows:
rundll32.exe shell32.dll,OpenAs_RunDLL %1
Close Regedit.exe