Deactivate OEM Key

Hi,

I've recently built my own computer, and have been able to bundle a copy of OEM Windows 7 Home Premium x64 with it, because I met all of MS's requirements for OEM.

However, I forgot to image my OS before I installed stuff.

Say a major problem arises a year or so down the track which forces me to wipe my HDD, will I be able to deactivate Windows so that I can reinstall it, or will I need to buy another copy?

Cheers,

rider_eragon