The software waranty is only 90 days -- so, it doesn't much matter.  However, if you do this you will have to call Microsoft to activate Windows.
Hai, may i ask some question about laptops? if i reinstalll the dell laptop from other source .iso and using product key behind laptop...its that void the warranty?if not using dell windows cd?sorry for my bad english 
Reformat windows will void warranty if not using dell windows CD??