[sfx1999]

Changing the BSP version does not work; I've tried it. You need to convert the lightmap and the texture lump. Each of the textures have a palette stored with them in HL, and in Quake they use the main palette. I am pretty sure that the lightmaps in HL are 24 bit also. They could be paletted, though.

Anyway, a texture in HL would be like this:

uchar r;
uchar g;
uchar b;
char *data;

Where as in Quake it would be:

char *data;