Oh damn, one of those computers.If i recall correctly, that's used to direct the air from the cpu cooler out to the front. Its awful, but we have them in some of our computers here.
Here is what im talking about

This is an old (2006) computer we have. Its not exactly what I thought, but this is what i mean. The black thing moves the air to the front case holes, which you can kinda see.
Also, the video card is a 6 or 7 series nvidia card. not sure which exact one, but its old.
2 200 GB HDDs, 2 (or 4) gb of ram
will sell for $1000 obo