CPU 100%

Hi My CPU has been running at 100% task manager showed ekrn.exe at 98%(which now doesn’t show up). I have tune up utilities so I used their system advisor which announced 7 programs were running abnormally high ST being 1 can’t remember the rest. Thus I decided to run their disc doctor which seems to have solved things! I just recently removed 140+ malware items via SAS ST & SBS&D are these programs subject to many FPs? My setup is xp2 ST(shield active), Boclean, CPF2.4(dep) & Nod32 3.0. Ideas of what went wrong much appreciated. Ekrn.exe just reappeared further down the task manger list at 00%