Why am I unable to access my removable drive on computers running Windows XP or Windows Vista when using the BitLocker To Go Reader?
The most common reason for this situation is that the drive is not formatted by using the FAT, FAT32, or exFAT file systems. To check for this, insert the drive in a computer running Windows 7, right-click the drive, and then click Properties to see the file format of the drive. Another reason could be that the system administrator has disabled access to removable drives from previous versions of Windows by using the BitLocker Group Policy settings. To check for this, attempt to access the drive from a computer running Windows XP or Windows Vista that is not joined to the domain.