I believe v7 defaults to CPU and GPU folding enabled.
"Note: Express Install (GPU & SMP) will automatically install one or more client slots to match the computer hardware detected. If multiple CPU cores are detected, an SMP slot is installed, otherwise a Uniprocessor slot is installed as the fall back option. If one or more GPUs are detected, one or more GPU slots are also installed automatically. If neither multicores or GPU are detected, a Uniprocessor slot is installed by default." link
"Try just CPU and see if that helps." - sounds good to me. And this is done how? I've installed it on my work PC to test (no slowdown, Win7 32bit) and can't find the option to turn GPC/CPU on/off. (unless it's part of the SLOTS options with -1)
Within FAHControl, you should see all of your slots. Right click on the one you want to change and you can pause it by clicking on "Pause". When you want to restart it, you can right click on the slot again and click "Fold".