You didn't understand what I said.
A 100MHz processor would not be able to run Vista because the processor itself would be the limiting factor, regardless of RAM. It would be at 100% load most of the time and still unable to get things done in time.
If you claim that "more RAM makes the CPU operate more efficiently", please let us all know how. The only possibility is that occasionally the OS has a choice between an algorithm that requires lots of memory, and one that requires lots of CPU... and is able to pick the one requiring lots of memory if there is extra. This is unlikely, however.
To reiterate: more RAM does improve the performance of a system, but it has very little to do with the CPU load or the CPU at all. Having sufficient RAM doesn't improve performance by reducing how often you have to wait on the CPU; it reduces how often you have to wait on the disk (and, while you're waiting on the disk, the CPU has no work to do). More RAM "makes the CPU more efficient" simply by not making it wait on work to do.
I'm not claiming that having less RAM makes a system perform better. I'm claiming that, if the poster is seeing high CPU load numbers, those are probably not due to a lack of RAM.
Try this. Edit a very large image in Photoshop/the GIMP, then open about fifty tabs in Firefox. You're putting enormous RAM demands on your system by doing this. By then alt-tabbing from firefox back to your image, you're creating a low-RAM situation and forcing your system to load the image back into RAM from swap.
Note that the CPU, during this process, sits mostly idle and probably at the minimum P-state. This is because there's nothing to do; everything's waiting on the image to get loaded back from swap. Not enough RAM, again, impacts performance because you're waiting on the disk, not on the CPU.
This fellow, however, has a problem with CPU use. If he meant "excessive swapping", he would have said that... unless he's confused about terms like CPU and swap and really meant "excessive swapping". Original poster, this isn't true, right?
Also, original poster: what process is using all of those CPU cycles? Your Dothan 1.73 is plenty fast.