I bought my desktop pc in 2007.it worked well during till last month but last week i downloaded harry porter movie from torrent.after watching that movie suddenly my computer becomes very slow.i thought that there might be some small problem .so i restarted my computer.but even after restart my computer remain slow.i thought there might be some virus in my computer .so i scanned my computer with latest Norton antivirus.but it didn’t detect anything than i removed my windows and reload a new window but still the problem is same.somebody help me out