For those of you who would like to see what's inside of those Hyperballoid .dat files, this program is for you. It functions similarly to DVUnpack (in fact, the base code is the one from DVUnpack).
Download here: http://www.mediafire.com/file/oakmdmejmtd/UnDATF.zip
Usage: Drag and drop a Hyperballoid .dat file (found in the game's directory) on to the program. The files will be extracted in a subdirectory with the same name in the source file's folder.
The interesting thing about this unpacker is the decryption part. I have never made an unpacker that decrypted before (without using external programs or slowing to the speed of molasses). Instead of recreating the decryption routine, I just took the developer's own decryption code (in assembly) and wrapped my script around it. That's why decryption is almost as fast as unencrypted file extraction. It's sort of ironic that I'm using their own code against them...
Bonus: Now DatBuild.exe can be decrypted, so you can create your own .dat files.
@Whiterabbit: Part 1 of Hyperballoid reverse engineering is done. I'm still trying to figure out whether the ball speed is hard-coded into the game or if it's controlled by any BSK scripts. (I haven't used your code yet, if you want to know.)
(And I forgot to set the right forum this post should go in. Whoops.)