my idea is to not to take risks using ur money to get keys from some websites (its cheaper, i know). buy the original os from microsoft certified partner or reseller in cmb. in that way, microsoft sri lanka will have your details and they will offer some discounts, events or even provide u with some freebees when a new os is out (generally they issue free upgrades from current os to new os)
This is the only legally valid MS license.
Good idea 
