my setup

i5-2300 nvidia gtx 550 ti 6 gigs ram 600 w ocz modular psu

recently reformatted and already experiencing drastic slowdown as soon as windows comes up, including repeated lockups with multiple various programs reporting that they are not responsive, then recovering after 10-30 seconds. ive checked memory and hard drive both of which come out fine. despite my plethura of worthless antiviral software im forced to assume that my illicit downloading practices have lead me into some comp trouble that i cant seem to determine. i have used ccleaner, search and destroy and malware bytes, all of which have found nothing to indicate what is causing this massive slowdown. in addition according to my resource manager my computer is operating at a load of only 30-50 percent CPU useage and 60 ram useage but taking 5-10 seconds to load files and open folders, and repeated lockups of multiple programs, especially firefox which seems to go unresponsive every 2-3 minutes. any help would be appreciated, i used a program called OTL by old timer, but cant make any sense of the results i was given. any help or suggestions would be appreciated, thank you for taking the time to read this

i have avast but it didnt even find anything when i had it do a full system scan, so im thinking its clueless(also nortons, avg, and ad-aware). i also have mse but it has yet to complete a full scan it takes so long (i left it on last night but when i woke up my computer had a problem and had to restart). my hard drive has 300 gigs out of 1tb open and i already used hd tune pro, which said my harddrive was fine and its not a ssd. also im a noob at comps and only have the hd that is currently inside the computer

in addition im not sure if studdering is the issue im suffering. my problem is that during my typing of these responses firefox has gone "not responsive" at least 5 times, each for times of about 5-10 seconds. when i try to control alt delete to bring up windows task manager it took 20 seconds. essentially its that my computer goes super slow at bringing up anything, or taking any action whatsoever that opens a program or file and has repeated incidents where i cant even click on whatever im trying to do because it locks up. the confusing thing about these incidents is that its right after restarting where there are minimal programs running and the computer and memory load is light.