How to change answermachine voices in fw .04.57

Hi everybody, someone have idea how to change the default voices in newst fw 04.57 for 7140/7170de? I would like to change theme with others, taked from asterisk or recorded by myself
The format is very strange for me, but the email attachment is in .wav format, and the stored message has no extension (rec.0.000).
Any suggestion will be appreciate and very helpfull
Thanks a lot
Tokka

Hi Bodega, thanks for your answer, and for the link too
I've done some test yesterday, and i found that the default answer messages are the fvp.00x, and recording a personal message on usb they assume uvp.0.00x, so it may be possible to rename these and overwrite the originals, but with the decoder it may be more easy...and powerfull
Thanks a lot, i go to make some test asap, and post in the linked topic
Thanks again
Mfg
Tokka