TC Replacing Player Sounds - Crashing?

[ShortBrass]

Hello there.
Sorry if this isn't the right section for my question, but the I guess I'm right.

So I was going to set up a Total Conversion, went after this thread, to make it fully isolate:
http://www.frictionalgames.com/forum/thread-11120.html


Next step for me, was to replace the players stepping sounds.
But after changing the destination sound files in the .snt's, I got a black blox, when I start to move in my TC
Is there something else, what should be changed?

Here's one of the .snt's:

step_walk_dirt.snt

<SOUNDENTITY>
<SOUNDS>
<Main>
<Sound File="step_walk_dirt_custom01" />
</Main>
</SOUNDS>
<PROPERTIES Volume="0.7" MinDistance="4" MaxDistance="12" Random="1" Interval="0" FadeEnd="False" FadeStart="False" Stream="False" Loop="False" Use3D="True" Blockable="True" BlockVolumeMul="0.7" Priority="0" />
</SOUNDENTITY>

I only changed the
<Sound File="">
nothing else.

Anyone knows what to do?