Whats the problem on slowing PC
Check your system requirements before installing any software. Its looks like you have installed a powerful antivirus software and it is creating problem in your system. Some virus in these days are also can cause this error but first you need to check the system requirements.
After you have checked your system requirements then check your program requirements and i am sure that there is some thing missing. Although you can also increase the memory in your computer but this is not the solution of your problem you need to install a software that really support your computer.
Also go to start and then to RUN and type cmd and press enter here type chkdsk and make sure that your disk does not contain any error. I hope you will be able to solve your problem.
Michal joran.