I don't know of one for files, but HobComment works great on
directories:
http://www.dr-hoiby.com/CommentExt/index.php
In some directories there is a file called descript.ion
This is an example of the content of such a file:
1.wav guitar solo 2005-05-14
readme.txt readme file for cubase
As you can see there are two file names, each followed by a comment.
When I hover over any of these files in my file manager I see that
comment as help text.
I use the file manager TC (share/nagware) which lets me add and edit such
comments for each file, but it is also possible to create such a
descript.ion file in a text editor.
I tried it in Windows Explorer and it doesn't work there. (I use win98se)
I renamed the descript.ion file to files.bbs, which is the other standard
system for adding comments to files, but that didn't work in Explorer
either, only in TC. (Explorer shows help text for folders though)
Is there such a system for files built into windows? I don't think so.
I never use Explorer myself so I don't know or care.
For me it works fine, adding comments to files by using TC, or by
editing a descript.ion or a files.bbs file.
TC (Total Commander) moves/copies the comments to the new folder
automatically when I move/copy a file to another folder.
I add comments to folders with Rainbow Folders or by editing the
Desktop.ini file in that folder. Rainbow Folders also allows changing the
color of the folder symbol.
I have different colors and icons for different folders, and help texts.
I change icon by editing the Desktop.ini file after I used Rainbow
Folders to create one. Or I open the colored folder symbol RF created in
a paint program and create my own folder icon from it.
File names are color coded so all .txt files are green, all sound files
have purple file names, all.exe files are red, etc..
and I can add comments to any file.
I like my colorful display in my file manager, and it helps a lot to see
quickly what types of files there are in a directory.
Conclusion: Use a good file manager instead of Explorer. I think this
file comment system is available in some freeware file managers too.
I think it is an old Norton Commander system and many modern file
managers are clones of NC.
I tried it in Free Commander, but it does not implement this, yet.
(Otherwise a very good freeware NC clone.)