Put your rtcw pk3 files in this folder.

The game needs at least these to work:

mp_pak0.pk3
mp_pak1.pk3
mp_pak2.pk3
mp_pak3.pk3
mp_pak4.pk3
mp_pak5.pk3
mp_pakmaps0.pk3
mp_pakmaps1.pk3
mp_pakmaps2.pk3
mp_pakmaps3.pk3
mp_pakmaps4.pk3
mp_pakmaps5.pk3
mp_pakmaps6.pk3
pak0.pk3
sp_pak1.pk3
sp_pak2.pk3
sp_pak3.pk3
sp_pak4.pk3