Fable running slow in Vista 32

Okay, I know my computer can run this game at max settings with good framerates. I'm running Vista Home Premium SP1 32 Bit OS.

I have a core duo 1.83 ghz t2400 processor, a nvidia go 7900 GS, 3 gigs of ram, and a 7200 RPM 16MB cache hard drive. I have the latest direct x.

Here's the minumum requirements:

• A computer that has a 1.4 gigahertz (GHz) equivalent or higher processor.
• Microsoft DirectX 9.0 or a later version of Microsoft DirectX. Microsoft DirectX 9.0c is installed by Fable: The Lost Chapters.
• 256 megabytes (MB) of system RAM.
• 3 gigabytes (GB) of available hard disk space.
• 32x speed or faster CD-ROM drive.
• 64 MB shader-capable video card.

I decreased the settings in the game to compensate. I went from 1440x900 to 1280x720, and lowered all the graphics settings down a notch from max. It did absolutely nothing.

The game ran pretty well in XP. According to Fraps, with stock settings, the game was running on average of 40-50fps, depending on what was going on. Overclocked, it ran around 60-70. It would always decrease in towns with lots of people walking around but it would never dip below 30. However in Vista, in towns, I'm lucky to be at 30 in high traffic areas. It usually dips to around 22fps (sometimes into the teens), and this is with the very same settings while overclocked. Outside towns, I tend to run at 45-55. I'm damned lucky to ever see 60.

This is a 2005 game and not graphic intensive these days. I had administrative privileges set to on and compatibility mode for XP. Did nothing. I did run Diskleaner and it did help a bit, but not enough to get me back to the fps I should be at.

I'm wondering, considering Vista uses more resources than XP, would a processor upgrade help? I'm thinking a core 2 duo t7400 2.16 ghz. Would this make up for Vista's higher requirements and make older games that weren't created with the OS in mind to work better? I ask this because Devil May Cry 4 works just fine in Vista and as fine as it did in XP, maybe even more so. So I know it's not just the OS.