Just a quick post for those who might be suffering from the same:
Microsoft Excel (2007, but perhaps any version) had for a long time been causing me a headache: The act of “Copying” or “cutting” any cell, in any file, would take a couple of seconds. The lag was driving me nuts. Google offered many possible solutions but not worked for me. What it came down to was ‘HD Agent’, some service relating to “Bluestacks”, slowing me right down. I disabled it from the windows task manager services and now excel is running well again.