Sorry to hear about your predicament. I don't think I can offer a real solution but, having had a degraded RAID1 setup, I might be able to answer a few questions and make some suggestions.
In my case the degradation occurred when a repair company installed a replacement DVD-RW and managed to get the drive letters mixed up. The contents of the two HDs became unsynchronised and the RAID array failed. However, as intended, the machine operated correctly on one disk, labelled C: as expected, while the second reappeared as E: and was visible and readable. It took me about a week to find out how to re-build the array, as the utility for this purpose available on booting-up did not work. In the end I was told of an alternative on the (Abit) CD which ran under Windows. I wiped the E: disk, ran this utility and all was fine.
So I suspect that the information on your good disk is ok - the chance that both HDs would fail or become corrupted at the same time is small (but not zero) and what you are up against is the extraordinary behaviour of WGA (Windows Genuine Advantage!) of not allowing you to operate your machine if it has a problem determining whether your copy is valid or not.
(a) why do you think that one HD is failing, rather than the disk contents became unsynchronized?
(b) did you try to rebuild the array at any point? On my system you can attempt to do this before booting into Windows by pressing the F10 key when invited so to do - unfortunately without effect, as I mentioned above.
(c) did you try operating with the faulty disk removed or switched off?
(a) could you mount the faulty disk as a slave in another (working) computer to see whether it can be read, and to run a scan and SMART tests to determine its stability?
(b) contact Microsoft; I believe there is a way round the 'failure to check licence' problem which they don't publicise widely as it might compromise Windows security
(c) I believe it is possible to remove or switch off WGA, at least temporarily. In fact I think I've seen a cooment on this forum to that effect, but haven't been able to locate it so far.