Reinstalled Windows XP Pro

The folders you mention are to do with the user accounts on your machine. Data stored in the "All Users" folder is available to every user, but data in the individually named folders e.g. "Anna" is only available to that user (and the administator of the machine I think).

Your "loss" of free space is probably due to the updates installed, especially SP2 if this was not previously installed, as that takes up approx. an additional 1GB of space. You may also have System Restore points, and also you might have installed additional features of XP Pro that were not there in the previous installation.

I would not advise deleting those folders straight off. Instead, go into Start --> Control Panel and then User Accounts. Did you do a clean install of XP? If not, old user account files may have been left. If there are user accounts there that you no longer use, you can delete them.

If you previously had an account called "Anna" and then after the reinstall created an account called "Anna/Greg" then the "Anna" folder may now be defunct. If there is no user account of such name in the User Accounts panel, you could try deleting that folder and there should be no problems. You might want to try deleting it to Recycle Bin first in case you need to restore it, and create a System Restore point.

The All Users.WINDOWS folder I'm not too sure about, certainly I don't have it, it may be a default WINDOWS folder for all users possibly.

Hope this helps,
Adi