Hi, everyone!
I have the same thing happening to my computer. I tried virus/spyware scan but it didn't find anything. When I tried Process Explorer it showed a 60-75 CPU. (Actually while im writing this post it is arround 40-60) I formated the harddrive and reinstalled the OS but still i have this high usage of CPU slowed down computer while System Idle Proceess is at 99. I thought it could be a problem that i have two particions: one i install my OS and all important drivers onto, and an other where i install other programs, games and save my important files. So I only formated the first particion because on the otherone i have a lot of data i need. But still in Process Explorer it shows high percentage for the Hardware Interrupts. I have only one router. I tried to do the things i read in this thread, but im from Hungary and my OS is in hungarian and my english was just not enought to translate all those special words

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I would be really happy if you could help me with this.