Not even Microsoft can do this reliably. It is a constant arms race as Microsoft updates WGA against people who seemingly have to do very little to bypass it. This is exacerbated by the needs of OEMs who (rightly) need to have preinstalled and prevalidated copies of OSs so they don't annoy their customers, whom may well be business customers. I think that a lot of the "hacks" around this have to do with OEM master keys.
Basically, pirating software (including Windows and your software) is a social problem not a technical one. The worst thing you can do as a software vendor (imho) is to annoy your legitimate customers in the quest to stop pirates to the point that you make your legitimate customers pirates. Example: some games have gone so far as to install rootkits as well as limiting the number of activations (eg Spore).
Limiting activations in particular is an evil practice. People have an innate sense of fairness about these things. If they have two activations of something, are running Windows XP and switch to Windows 7 RC and will then switch to a real version of Windows 7 when released then they've just gone over the limit. As in the case of Spore, you can request additional activations over the phone but this kind of thing just rubs people the wrong way. Some to the point that they'll feel quite justified in bypassing such restrictions.
As for downvoting your question, I suspect it's because people don't like your intent, probably for reasons that are similar to the ones I've listed above.
