Windows OS from Xp To 7

Hi.

I just want to format my HP desktop HD with Windows Xp pro and upgrade it to Windows 7 with the same hardware.

I have Norton internet security 2010 with 3 Pc activations key licence and i used allready 2 of them.

Can i reinstall Norton and this count like another activation?

If not should i unistall Norton before format and reinstalled again with the new OS?

Thanks for your help in this.

Ernesto