Thanks to all who replied,
I just did some maintenence; scan disk, Spybot Search and Destroy scan (removed usage tracks, setup logs etc.), defrag (only 6% fragmented), and scanreg /fix /opt and my 3dMark score is back in my normal range, so maybe this update didn't cause me any problems after all.
RESULTS
3DMark Score 6851
Game 1 - Car Chase - Low Detail 88.0 fps
Game 1 - Car Chase - High Detail 28.3 fps
Game 2 - Dragothic - Low Detail 137.7 fps
Game 2 - Dragothic - High Detail 77.2 fps
Game 3 - Lobby - Low Detail 84.8 fps
Game 3 - Lobby - High Detail 38.4 fps
Game 4 - Nature 43.5 fps
Fill Rate (Single-Texturing) 865.7 MTexels/s
Fill Rate (Multi-Texturing) 1904.4 MTexels/s
High Polygon Count (1 Light) 41.3 MTriangles/s
High Polygon Count (8 Lights) 10.2 MTriangles/s
Environment Bump Mapping 128.3 fps
DOT3 Bump Mapping 121.0 fps
Vertex Shader 81.5 fps
Pixel Shader 99.8 fps
Advanced Pixel Shader 71.2 fps
Point Sprites 25.4 MSprites/s
Still haven't tried the unofficial patches yet, but plan to do so in the near future.
Maybe I'll try extracting the older gdi32.dll also sometime.
Thanks again.