Fresh install - now a bit of trouble with datafiles...

I have a PC with two SATA drives - one for the OS and programs and the other
for data files, i.e. music, documents and pictures. I also use the second
drive for the 'important' data files such as the Outlook *.pst and the
Favourites menu. The plan was to be able to reformat the primary drive when
necessary and leave the secondary drive intact. Both drives are formatted as
NTFS.

I understand the files won't necessarily be accessible by a user with the
same name and password, but I've been doing this for a while and I may have
got my knickers in a twist.

What I think I need to do, if possible, is remove the security and/or
ownership settings on all the files, or change the details to relate to the
appropriate user. The PC isn't particularly secure and only my wife and I
use it, but I don't want to accidently see her files and I don't think she
would want to see mine - especially as it's approaching Christmas!

Am I being a numpty, or is there a way I can achieve this, or do I need is
an idiots guide to setting up WinXP security?

Thanks in advance.