Here's some settings to start off with

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Plugin: Pete's OpenGL Driver 1.1.75
Author: Pete Bernert
Card vendor: Microsoft Corporation
GFX card: GDI Generic
Resolution/Color:
- 640x480 Window mode
[32 Bit]- Keep psx aspect ratio: off
Textures:
- R8G8B8A8
- Filtering: 0
- Hi-Res textures: 0
- VRam size: 128 MBytes
Framerate:
- FPS limitation: on
- Frame skipping: off
- FPS limit: Auto
Compatibility:
- Offscreen drawing: 2
- Framebuffer texture: 2
- Framebuffer access: 3
(You might want to try 1 and 2 also)
- Alpha multipass: on
- Mask bit: off
- Advanced blending: on
Misc:
- Scanlines: off
- Line mode: off
- Unfiltered FB: off
- 15 bit FB: off
- Dithering: off
- Screen smoothing: off
- Screen cushion: off
- Game fixes: off [00000000]
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Main PC:
Asus P6T Deluxe, Intel Core i7 920 C0 @ 3.7 GHz (195x19, 1.3v core, 1.84v PLL, 1.3625v uncore) w/Thermalright Ultra 120 Extreme, 3x2 GB G Skill PC3-12800 @ 780 MHz, 7-7-7-21-1T, 1.66v; ATi Radeon HD 4870 1 GB @ 790/1000 w/Zalman VF-1000, 300 GB WD VelociRaptor, 4x500 GB WD RE2 (RAID 10), 3ware 9650SE-4LPML RAID controller, SB X-Fi Titanium, Seasonic M12D 750w, CM Stacker 810, Windows 7 Pro 64-bit, Dell 2007WFP
XBL/PSN/WoW: Thordrune