Depending on your copy (read your EULA) you could even not have the ability to install it again.
Most Windows licenses allow you to have it installed on two machines simultaneously (like your PC and your laptop).
So (older) ones, don't allow this.
Others are like student trials or OEM limited licenses that allow for only 2 activations and then it's worthless.
Read your EULA, and if worst comes to worst...you can just try it and see what happens. If it activates, it activates. If it doesn't, it doesn't.
You should be fine. Relax, and be smart.