will a 6600 intel on a p5b 32 bit system run a hd6950 efficiently or at all . I have some older parts lying around .

Sure, why not. I have a Q6600 feeding a HD 6970. I run MW@H and sometimes E@H. Also have a E8500 feeding another one too. Both are W7 64bit, but that shouldn't matter.

Run 2 WUs at a time for MW@H. I try and keep them not in sync so they are not using the CPU at the same time, but that's cause I run WCG with 3 cores and leave 1 core for MW.

The 6950 will run just fine.
To get the most out of it though you should consider running multiple WU at once. I have found on my 6950 that running 8 wu at once provides the best results.
There is a thread in this same forum about running multiple WU at once.
My app config looks like this:

<app_config>
<app>
<name>milkyway</name>
<gpu_versions>
<gpu_usage>0.125</gpu_usage>
<cpu_usage>0.125</cpu_usage>
</gpu_versions>
</app>
</app_config>

thanks guys