As administrator (X) you have access to all files and applications. However what level of access did you give for Y and Z? If less than 'admin' access, and your photos stored under X, you are not 'permitted' to access X files (or applications in theory).

Two options
Go to System preferences > Accounts > either under Y or Z, see if "Allow user to administrater this computer" box is checked. If not, check them off and you'll see any and all of X files/apps

If you don't want to give Y and/or Z adminstration privileges, then you need to load pictures separately under one of these two accounts and then only that account plus X will have access.

For lots more details, suggest you consider purchasing these two eBooks from http://www.takecontrolbooks.com/

1. Taking Control of Users and Accounts in Leopard (will work for Tiger too)
2. Taking Control of Sharing Files

Both are $5 (or $10) each?


PS - re nano problem, i would take to genius bar for them to troubleshoot; that way, you then have on record reporting this problem....maybe need to get 'replacement' from apple.