my desktop pc has windows xp sp3, ive taken all internet security off it, and tried to download, mcafee, avg free, norton and they all just stop, mcafee i had a disc and it wouldnt even run it. and ctrl alt del brings up window, click on task manager and nothing ive tried everything to get it to open and it will not. can someone help please

Run rkill, small executable, no need to install. READ THE DESCRIPTION. Download them all, and run in turn until one works. http://www.bleepingcomputer.com/download…
After rkill, run a full scan with these two programs:http://download.cnet.com/Malwarebytes-An…http://download.cnet.com/SuperAntiSpywar…