Yes, but the answer depends on your configuration.
The first question is how powerful of a security mechanism do you need
it to be? Are we talking nuclear secrets here or plans for a surprise
birthday party? In general, anyone who has physical access to a
machine has the ability to defeat almost any security mechanism
employed on it. By adding layers of security, you just make it take
longer, but there is not really a guaranteed way to completely secure
it.
Second question: Do other people use your PC using the same login
user ID that you use?
1. If no, then they are using a different ID, then you can right
click on the "My Documents" folder and select properties, and then
check Advanced, and then check "Encrypt contents to secure data". You
may have to navigate to the My Documents folder through the "C:
\Documents and Settings\Your User ID\" to get to the correct menu.
2. If the answer is Yes, then stop doing that and go back to answer
#1. The security you ask for is built into the operating system. Use
it by defining separate logins for each user.
3. If the answer is still Yes, then it gets trickier, because you are
disabling the most powerful security mechanisms that are built in.
You can secure individual office files within each of those programs
so that a password is required to read or write them. With pictures,
there isn't anything built in that I know of. You may have to use a
3rd party encryption program to encrypt the contents. PGP is an
example, but I personally haven't used it for this purpose.
Post a clarifying question if you have any trouble.