Dual boot ? seeing documents on HDD

I believe that it is booting to the second instance. If the first instance is on the C: drive, and you can navigate to the C: drive I believe that you are seeing all of the files on the C: drive regardless of boot instance. I assume that the second instance was installed to a partition? All that means to the computer is that it boots to "D:" instead of C: but C: is still an accessible partition.

Hope this helps

I think the Windows is booting to the second installation. The default boot is always to the latest Windows. Further evidence is that you are not getting BSOD or stop error (at least you are not telling us).

Open boot.ini from C: (from Windows Explorer, Tools > Folder Options > View > check on Show hidden files and folders, and uncheck Hide extensions for known file types and Hide protected operating system files) and check which system directory and partition each Windows got installed.

If the second Windows got installed in C:, the system directory would be different from the first one (Winnt or Windows). However, the two Windows would share the same Documents and Settings, and Program Files folders. And if you expand the Documents and Settings folder, you would see all the user profiles from both Windows. Depending on the security settings, no password for a user login, for example, the user?s documents can be seen and accessed.