One program that can be help as far as getting everything updated as well as point out security risks would be the Secunia Personal Software Inspector (PSI)
That will prompt you on everything it finds however that sees something new available.
Besides tightening security the updates for various things can also help any system run smoother as well. With the cpu being tasked on and off getting a little stormy at times you might want to "batten down the hatches" a little to see if this will clear things up for you.
When looking at how much the quad core sees here the max so far with a good load comes in about 30% with a particular Steam title that saw that. The explorer.exe errors seen here recently started appearing due to the need for an overdue clean install of Windows. Between any possible registry errors and fragmented files you can run into the same thing at times.