dual boot with accessibility options

I bought a system with 500 gb hard drive on which i installed windows xp on c drive of 40 gb. D is of 40 and rest is in E.

After that with the help partition manager i extracted 40 gb from e and made a separate drive m on which i installed windows 7 preview.

Now i want to install another operating windows vista ultimate and i want to set accessibility options so that windows vista and 7 should not be able to access any other drives making my system less vulnerable to viruses as windows 7 is beta version.

And also tell me how to uninstall operating system one by one.

Hello , I think What You need is a Good Disk encryption software

Check this for more information
PGP Whole Disk Encryption
Proactively secure confidential data on disks and removable media



PGP Whole Disk Encryption provides enterprises with comprehensive, nonstop disk encryption for Microsoft and Apple Mac OS X, enabling quick, cost-effective protection for data on desktops, laptops, and removable media. The encrypted data is continuously safeguarded from unauthorized access, providing strong security for intellectual property, customer and partner data, and corporate brand equity.

• Easy, automatic operation–Protects data without changing the user experience.
• Enforced security policies–Automatically enforce data protection with centrally managed policies.
• Accelerated deployment–Achieves full disk encryption using the existing infrastructure.
• Reduced operational costs–Result from centrally automating encryption policies.

As a PGP Encryption Platform-enabled application, PGP Whole Disk Encryption can be used with PGP Universal Server to manage existing policies, users, keys, and configurations, expediting deployment and policy enforcement. PGP Whole Disk Encryption can also be used in combination with other PGP encryption applications to provide multiple layers of security.