New Lenovo Z70 running slowly?

About a week or two ago I bought a Lenovo Z70 laptop. It has an intel I7 core and 16gb of ram. Recently (the past few days) it has actually been seeming pretty slow performing basic tasks, like opening a video or audio file. Seeing as it's a newish computer with a relatively clean hard drive, a good core, and plenty of ram this surprised me when it started happening. I do download a lot of stuff off of the internet, so I was thinking maybe I got a virus of some kind ( even though I do have an antivirus program). Does anyone have suggestions on how I could clean up/speed up my computer?

Run malwarebytes anti-malware, also check out the software burn in test and have it stress test your RAM, and you can also use something like CCleaner to clean up any temp files and general clutter, registry scan, and clean up the start-up programs. Any of those will help you out.