I decided to clear pagefile.sys so I set HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager\Memory Management\ClearPageFileAtShutdown to 1 and rebooted OK. However Recuva in standard scan now runs stage 1, with the number of files found increasing as normal, but ends immediately in stage 2 with No Files Found.
In debug mode this appears in the log: WinAPI exception: FileDriveImpl.cpp(140) : The parameter is incorrect.
I have reset the registry key back to 0 and rebooted and the same happens, no files found.
I knew I should have kept my fingers out of the registry!