by "cleaning" he might have meant did you run a "defrag", clean up unused icons, folders, remove pix to a disc or thumbdrive,, could have meant anything...
all are MUST do's twice a year my son says...more if you actually USE the computer for more things..like photo storage!, website storage(your faves)...they all take up space and all make the puter run slower over time!
all those icons on your screen..take up space...
once a month I do a cleaning...I pitch old bookmarks, sites that no longer interest me, pix go on a disc and on my external hard drive, patterns get either printed or ditched..it takes a whole Sunday afternoon.
Then every 3 months my son comes over and opens my tower to clean it out for me!