Get WinZip. When you zip with WinZip, you can choose the compression settings (and therefore, tell the program to NOT compress your files).
It's not a free program, [moderated]
Working on the upload... EDIT: ... and here it is!
Sprint_bootanimation.zip
Just stick that into /system/customize/resource (while /system is mounted as r/w!), and confirm the overwrite.
Reboot and see what you get.
** If it doesn't work, go back to the file and change the permissions to look like the image I posted earlier ^^