Looks like Microsoft has more work to do on Vista's security. According to InfoWorld:
After security researcher Joanna Rutkowska demonstrated Thursday how it's possible to circumvent security in Microsoft's Vista beta software and install a rootkit called Blue Pill, Microsoft said it intends to find ways to stop both potential threats before Vista ships. At the Black Hat conference, Rutkowska, security researcher at Singapore-based firm COSEINC, showed that she found a way to bypass the Vista integrity-checking process for loading unsigned code into the Vista kernel. Then she presented Blue Pill, a rootkit she created based on Advanced Micro Devices (AMD) Secure Virtual Machine, Pacifica.