Password File Protection Windows XP

I am trying to set file permission for folders in Win XP but it seems that the only way to have file protection is to purchase a seperate software.

The purpose is i am sharing a wireless network and do not want others to access my banking information or even mess around in one of my computers.

I have gone into the sharing and security and set a file to share and to allow file changing (b/c i access this desktop computer from a laptop) but there is no option to have a password like in win 98.

Is there a way to set a password just to access a file - something that is simple like in Win 98? I have read many forums about simple file sharing but there are no options in properties or shaing and security for password protection.

Thank you for your time,
FRUSTRATED

If it's in a folder that you checked the 'Make this folder private' option they shouldn't be able to see it. I know I can't in my little network. But if you absolutely want a password, then I don't know.