The fps drops to 10 immediately after enemies show up now. In your prior demo the fps never dropped
This probably has to do with the "texture changes" you made recently. SO whatever they are, I'd remove them. I have Directx 9c that I installed from a very recent game demo (Lucas Arts RTS game) - I think it was the same as the Quake 4? Or was quake 4 coming with Directx 9b. I'll verify my DirectX driver but I SERIOUSLY doubt that's the problem.
System Specs:
AMD Athlon(tm) XP, 2500+, MMX, 3DNow, 1.8GHz
1024MB DDR RAM
DirectX 9.0c (4.09.0000.0904)
Video Specs:
GeForce 6800 GT
256 MB
DirectDraw Acceleration: Enabled
Direct3D Acceleration: Enabled
AGP Texture Acceleration: Enabled
What's your DirectX Version? Everything Enabled? Click START -> Click RUN -> Type "dxdiag" and HIT ENTER.
REGARDING THE BLACKBOXES
All I can say is, why is it that the PLAYER'S lasers dont have black boxes, the enemy spikes guys dont have black boxes but all others do? (including coins and enemy lasers/missles) - You either are A) Rendering them differently or B) They have in fact, transparent backgrounds in their direct art files.
BLACKBOX WORK-AROUND
One thing you could do to solve this problem is go directly to your Art!! What I would do is edit the art files, and change them to a PNG and directly modify the black to a transparent background. That means they wouldn't be black, green, purple, or whatever some people use for "transparency" but they would be in fact transparent regardless. The sprites in my game are transparent in that way, instead of having any colored backgrounds.
Some people use colored backgrounds and have their program render the color to transparency. But you don't have to do this anymore with the latest PNG Technology.
Some people use BLACK backgrounds and use "additive blending" or "light blending" but that doesnt look good for sprites, its good for particle effects and explosions though.
OH come to think of it!! Your explosions are transparent as well....
Side Note:
I really think you should change your player ship, it just looks blockier than everything else, are you scaling it up or something? Also the missiles dont act like real missiles at all, Their Y coordinates change suddenly, sometimes they all look like they're on the same Y coordinate and it looks un-missile-like.