You can also set Boinc to NOT use all the cpu's for crunching at the same time. If you change it to only use 75% of the available cpu's your pc will become more responsive. Using ALL of the cpu's AND your gpu can make the pc slow to respond as there is nothing left to run the pc until Boinc recognizes that you want to do something besides crunch and backs off. It WILL back opff, but as soon as you stop needing cpu for something else, for instance as soon as a spreadsheet loads, Boinc ramps back up and then must back off again, this is probably the lag you are seeing. There are SEVERl tweaks you can make to Boinc but fist try the 75% of available cpu's and see if that helps. Your gpu will MORE than make up for the lost cpu crunching power and you may 'get your pc back'!