Norton Internet Security is not installing

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.