How do I get a registry value in Inno Setup when the value only uses the default name?

I'm trying to get the install directory of an application from the Windows Registry (Google Sketchup in this case) with Inno Setup's Pascal scripting so I can install a plugin there.

The registry key doesn't have a name, it just has "(Default)" in Regedit.

I tried this:

RegQueryStringValue( HKLM, 'SOFTWARE\Google\Google Sketchup 6', '(Default)', pluginLoc );

but it doesn't return a value. Any suggestions?