This is a short tutorial on how to save your animation as png in Windows XP
First get the official plugin added below in attachments.
Extract the files and you will have two files, your plug-in > file-apng.exe and file-apng.ui
Open your (C:\Program Files\GIMP-2.0\lib\gimp\2.0\plug-ins\)
look for the file called "file-png.exe and remove that.
[Before you remove it, back it up or save it somewhere just in case you need it back.]
After removing, place the two files that you just extracted into that folder.
If you happen to have Gimp open, close it then re-open
You should now have everything you need to make animated png images.
Open Gimp, make an animated image or open one you already have.
Save as filename.png.
A window should open that looks like this.
Make sure the animation is checked, then click export. You should now have an animated png. Try opening it again with gimp and you should have your layers and it should be animated.