Creative ADPCM

Hi.

I’m trying to replace the english voices in an old game for spanish voices.

I discovered the codec these samples seemed codec with Creative ADPCM. Then I downloaded these codec from ftp.mplayerhq.hu/MPlayer/samples/A-codecs/Creative%20Audio/

After install it, I extracted a sample from the original game with a hexadecimal editor, I appended it to a RIFF header with the CTADPCM format tag and I played it.

It was played correctly but overdrived.

How the old programmers coded these samples? By software or hardware? With what tool?