system
3
It is a virus because
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It was not there 4 days ago and taskmanager works after the pc boots
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It attacks after a considerable amount of time
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All the above functionalities work at the time of boot but not after the boot 
As u suggested i did run the avast boot time scanner n detected a trojen in my exporer.exe and untill now it has not affected yet . So i am hoping it was that trogen but i just wanted to know the name to get more information abt it
Well Thanks for the advice
nitish