Please give details of laptop, operating system and what programmes you are running inc. What virus scanner you are using, then someone may be able to help you.
Briefly, I would suggest that if you have a bundle of programs all open at the same time, then they are all clogging up your RAM memory and reducing the available operating space.
Either reduce the number of programs running or increase your RAM memory.
Have you tried defragging your hard drive? Might be worth a shot if you haven't tried that yet. You might also try cleaning your PC registry. Often a DLL error will cause your PC to run slow. I recommend using PC Health Boost as a registry cleaning tool: http://www.pchealthboost.com/blog/