Installed memory: 3.00 GB (2.74 GB usable).
That sounds adequate to me.
I would still shut down all windows except for Malwarebytes and see if things speed up.
Just read post 50 and having HWMonitor installed is a great idea to see what your processor temps are running, things go to crap as you approach 100 C.
I have it installed on the new machine and it's a handy monitor to make sure things are running cool, especially with laptops and their marginal cooling to start with.
I don't think 3.0 GB of RAM is enough any more, not with Win7. Right now, this computer is running Firefox and Outlook, with Kaspersky running in the background and is using 2.45 GB of RAM.
If you can, upgrade to a min of 4 GB, preferably 8 GB. More is better. Going from 2 GB to 4 GB fixed that same problem on my old Dell laptop when I switched it from XP to Win7.
Have you checked your performance score? It would be interesting to see what it says.
Also? You might find a program like Auslogics BoostSpeed helpful, as they contain all sorts of speed enhancers, registry cleaners, defragers, etc., all in one package.