Q: Can I open files that are stored on a BitLocker-protected USB drive from my Windows XP or Windows Vista system?

A: Yes, this is possible thanks to the BitLocker To Go Reader application that Microsoft provides. The BitLocker To Go Reader (bitlockertogo.exe) is an application that works on computers running Vista or Windows XP, and allows you to open and view the content of removable drives that have been BitLocker-protected in Windows 7. It allows people using Windows 7 Enterprise Edition or Ultimate Edition to share their BitLocker-protected data on USB drives with anyone using Windows 7, Windows Vista, or Windows XP.

The BitLocker To Go Reader doesn’t allow you to encrypt drives using BitLocker or add files to an encrypted drive—it just lets you read files on an encrypted drive. When you encrypt a USB drive using BitLocker, the BitLocker To Go Reader application is automatically added on an un-encrypted part of the drive.

The BitLocker To Go Reader requires a password to unlock an BitLocker-protected drive. Once the drive is unlocked, you have read-only access to the files. If you want to edit the files, you must copy them to another drive on your computer. By doing so, the files will no longer be BitLocker-protected on the new location, but they will remain protected in their original location.

When you plug a BitLocker-protected drive into a Vista or XP computer that has AutoPlay enabled, AutoPlay will give you the option to automatically run the BitLocker To Go Reader. If AutoPlay isn't enabled, you can start bitlockertogo.exe by opening the removable drive from Windows Explorer.

The BitLocker To Go Reader only works on Vista and XP for drives that have been BitLocker protected using a password. If your drive is BitLocker-protected using a secret that's stored on a smart card, you won’t be able to use the BitLocker To Go Reader.

To use the BitLocker To Go Reader on a computer that runs Vista or XP, your BitLocker-protected removable drive must be formatted using the exFAT, FAT16, or FAT32 file systems. If your drive is NTFS formatted, it can only be unlocked from a computer that runs Windows 7.