Castlevania: SotN

Okay, I'm pretty far in to the game but I've been noticeing some slow down. Its usually when I kill something it starts to burn up and slows. And when I turn in to mist it slows down. I dunno its wierd.

Specs:
AMD Athlon 64 Processor
3000+
2.00 GHz, 1.00 GB of RAM

Video Plugin Configuration:

Plugin: Pete's OpenGL Driver 1.1.76
Author: Pete Bernert
Card vendor: ATI Technologies Inc.
GFX card: RADEON 9800 Pro x86/MMX/3DNow!/SSE2

Resolution/Color:
- 1280x1024 Fullscreen - NO desktop changing [32 Bit]
- Keep psx aspect ratio: off

Textures:
- R8G8B8A8
- Filtering: 6
- Hi-Res textures: 2
- VRam size: 0 MBytes

Framerate:
- FPS limitation: on
- Frame skipping: off
- FPS limit: 60.0

Compatibility:
- Offscreen drawing: 3
- Framebuffer texture: 3
- Framebuffer access: 4
- Alpha multipass: on
- Mask bit: off
- Advanced blending: off

Misc:
- Scanlines: off
- Line mode: off
- Unfiltered FB: off
- 15 bit FB: off
- Dithering: off
- Screen smoothing: off
- Screen cushion: off
- Game fixes: off [0001d000]

I dunno do you think I should allow more frames per second? Thanks for any and all help and advice.