Well I can tell you guys what happens after you try and activate the system more than 3 times using a standard oem disc.
My parents live in a area with a lot of thunderstorms and lightning, and every so often it will hit the house and kill something, they have tried everything from surge protectors to U.P.S, but if you have to replace them every two months or so, its just not cost effective, especially UPSes.
In a two year I had to replace the motherboard in one of there pcs 4 or more times (covered under insurance luckily) each time re-installing windows as I couldnt get the exact board they had, after the 3rd online activation, it would just refuse to activate , and you have to call Microsoft with a reason why your installing windows on a "new system" so many times, each time I had to explain why, (lightning damage to motherboard) but they will allways have me read out the phone activation code and give me the long activation code, without any hassle 😀
So as long as its a normal non-vendor O.E.M and your prepared to phone in its not a problem...
PS this is in South Africa though, but it sounded like the call was forwarded to a international call center anyway so it should be the same.