until dec 2010 my computer was running fine when something happened to my pc.and then a computer which was running fine about 2 hrs ago before it was exposed to internet without a fully functioning anti malware suddenly started to malfunction.like if I would open any game the computer would restart and even if I fullscreen a video it would restart.so I formatted only c: and reinstalled windows.but again the same problem.then I wiped out my hard disk and reinstalled os then the problem solved but with two striking changes, first was aliasing of games which didn't happen before under same hardware and software settings.and the cpu fan which started to produce unnecessarily extra noise than before and it speeds up very high for 3 secs and then down for about 1.5 secs and repeats, which was constant before with almost no noise at all.after two years in 2012 the mobo was gone.so I replaced the entire system except monitor keyboard and mouse.but the problem not solved even then.i didn't use any thing that was from previous system like usb drives.but before I bought new system I noticed something.i had some backup dvds which were burned in 2009 a year before.they wre used by me and some friends between 2009-2010 without any issue.but once I used them after getting this problem and then gave it to my friends then they started to have same problems as me.then I thought the only way this could happen was that there is a dangerous program in my system which had the ability to transfer itself to already burned dvds and from them it would copy itself to which ever computer inserted and hence the same problems bcause there was absolutely no other way I can explain it.and about cpu fan speed's fluctuations,i once disconnected all the cables inside and outsie the cpu cabinet except power cable and then turned on the computer the fluctuation was still there even when there was nothing very big to process cuz harddisk cables and dvd drive cables and even monitor, mouse,keyboard were disconnected.so can anybody explain this to me?Can this be figured out and solved?what should I do now?