EDIT 10/20/2011:
The problem I was having below was caused by trying to install Python(x,y) after ArcGIS 10. I got a new machine yesterday and instructed IT to install Python(x,y) 2.6.5.3 (has correct numpy version for Arc). I had them run a non-scripted installation of ArcGIS 10 so we could make sure the installer didn't try to give us a second version of Python. I now have a single Python directory and ArcPy works (so far); as of right now I'm considering this issue resolved.
I have what would seem to be an issue with a clear and easy answer, but so far I haven't been able to find a suitable one.
Here is the situation:
I need to have both ArcGIS 10 and Python(x,y) installed on a server that is accessed by multiple users in order to accommodate everybody's needs. Because both of these pieces of software install their own version of Python 2.6, the libraries installed by one cannot be accessed by the other. In other words, if we install ArcGIS before Python(x,y) we can use all of the goodies like MatPlotLib, numPy, etc., but the arcPy module is unavailable and vice versa.
To solve this problem I tried adding the path to the various libraries to the python path of the "active" version of Python to no effect, ala this thread: Problems setting up eclipse (with PyDev) for ArcGIS 10.
We could possibly resort to installing ArcGIS 10 and then try to manually install all of the libraries that are included with Python(x,y), but this would not be an ideal fix. Alternatively we could install ArcGIS 9.3.x since that comes with Python 2.5, but I would prefer to have all of the functionality that is available with the new arcPy module. If someone out there has already encountered this and has any other suggestions I'm all ears!
We are working in the Windows Server 2008 R2 environment.
Best Answer
So you're using the version of Python(x,y) with Python 2.5 and ArcGIS 10, which uses Python 2.6? If this is the case, it will not work regardless as Python extensions written in C are not binary compatible across versions.