your 800x600 texture still takes about 2mb (if its a 32bit image), so thats one thing to think a bout, as saberdude said, one solution is to texture a box or sphere with your bitmap, then turn off culling for that object (so that you can see it even when you are inside it) resize it realy big (but within camera range) and turn the objects sensitivity to light off, that should do it.
Mentor
PC1: P4 3ghz, 1gig mem, 3x160gig hd`s, Radeon 9800pro w cooler (3rd gfx card), 6 way speakers.
PC2: AMD 2ghz, 512mb ram, FX5200 ultra, 16 bit SB.
Mini ATX cases suck.