Hi Lefteris,i guess you are generating a Key, based on a special hardware-component. You could couple this Key with a valid e-mail adress and password in case one needs a replacement of the key.I.e. i bought a new motherboard (faster CPU for demanding products "hinthint") and a new HD, because this one i am running is producing more and more corrupt sectors, so if i had just installed your 737NG i would probably run in exactly the troubles you are describing.Cheers and best regardsHolger