File encryption - How to utilize

I am experimenting file encryption(vista buit-in functionality) for the
purpose of securing data when theft of PC box occurs.

My PC is triple-boot system for WVT, WXP and W2k. With each OS there are
two user accounts being "Administrator" and "XYZ" who is in
Adminstrators group. Unique password is set for each of the two users
but the same passwords are used for all three OSes.

On WVT, XYZ user encrypted a test folder named as Testfolder that
contains one test file named as testfile. Encryption was not let
propagate to the file contained in the folder.

Then I reviewed the effect of the encryption and found that the file
could be accessed(opened) by any one of the two users on any one of the
three OSes.

My questions is if I can generalize the above results as follows:

1) Any account holder with an OS can access encrypted folder/file
regardless of who encrypted it.
2) Whether being able to access an encrypted file depend only on
password and not on OS on which the encryption is done.