you could try to defragment your hard drive if u have alot of files in it...... do it even if it has a small amount of files........aslo check your mb manuel or the website for info on the type of ram it supports.........also u should know that different brands of ram don't "mix" well with others....eg if one stick is samsung, then the other should be sumsung also.
Last but not least you should take a look at your task manager on the "process tab" and note all the different processes that are running. If u see any strange process that your're not sure about use google to find out what it does!!!!..good luck..