I purchased Norton Internet Security in the computer sales shop. They gave a CD and Product Key in the sealed cover. I installed in computer then I updated, and I utilized power erased also. After some days some suspicious Virus found. Again I Power erased tool but not removed. Then I re-installed X P with partition. After that all virus removed from my computer. Then I re-installed Norton but is not installing and showing "An error has occurred" What can I do? please do the needful.