There's already been a workaround discovered
for using a Vista
upgrade DVD to perform a full install, but some intrepid hackers now appear to have opened up an even bigger flaw in the shiny new OS's armor, developing a brute force keygen that spits out valid product activation keys. While the keygen has been confirmed to work by a number of sources, it's hardly a quick-and-easy hack, requiring some significant horsepower and quite a bit of patience, needing anything from a few hours to a few days to churn out a key. Not to mention the small problem that Microsoft could seemingly stop this particular hack in its tracks relatively easy. As ZD Net points out, however, the keygen could very well cause some additional headaches for Microsoft once the keys generated start overlapping with those already out there in legitimate copies of Vista, presumably leaving anyone who picks the wrong box out of luck.
[Thanks to everyone who sent this in]