Matplotlib on Windows installed via the latest binary for Python 2.4 (matplotlib-0.90.1.win32-py2.4.exe)
complains about not finding the Microsoft C runtime (MSVCP71.dll). Reading the microsoft documentation about this DLL it seems that matplotlib should be including it in the binary package above.
I usually install the Python 2.5 version on a Windows machine that has Visual Studio and personally have not run into this problem, but ran into it when installing on a User's machine.
I don't recall seeing this on matplotlib.sf.net. Perhaps it is a known issue.