Frankly, I would reformat and save myself the heartache. If it's something that CCcleaner and Spyobt can't fix (I'm not one for securtiy programs) I would reformat. I've torrented mass amounts of Data nearing 10TB at this point... Never a signle virus.
Does you laptop have bloatware and bullcrud programs such as norton antivirus? If so, I would uninstall those first. There could be conflicting security systems. Exl; if you have AVG and Norton or any other two security systems on the same computer it will be unavoidably, unobtusively slow. Antivirus programs do NOT like each other... Ever.... I just abandon all of the uneeded pos's. ; )
Other than that I'd just try my set of trusty programs... if not.... reformat. Although, some laptop makers do not allow reformat on their boards. (They put retarded bios flashes on their boards to prevent even subtle creativity and lock you into their bloatware and their system). I bricked my Gateway core i5 larppy top a while back doing this... Checked the HD for bad sectors (I thought it had something to do with buying a prebuilt computer) and violla! I had discovered I had bricked my HD....
Idk, I would reformat... Because if it's an enexplicible slow you're likely to just knock your brains out and become VERY frustrated with it....
It only takes half an hour. Just back up all your startup programs and Music files / etc.
You'll be back to exactly how your desktop / computer runs now within 1 30 mins... Even if your computer is as inundate and overpopulated as mine... This is where it helps to have multiple drives (a boot drive in a computer) and a external drive you can use to aid your laptop...