On page 113 for WRITEVALUE

Quote:
Subkey
Identifies the subkey where you want to write a value entry.
Entry
The name of the entry. To write to the default entry of a key, specify an empty string as the entry name ("").


I also think you have the WRONG key listed. Here is what I think the code should be.

Code:
Break On
Dim $RC
$RC=WriteValue('HKCR\.tif','','IDMViewerApp.Document',REG_SZ)
'Reg update returned: ' + @ERROR + ' - ' + @SERROR ?


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