如何使用distutils安装到特定的Python安装？

I have a Windows machine with Python 2.3, 2.6 and 3.0 installed and 2.5 installed with Cygwin. I've downloaded the pexpect package but when I run "python setup.py install" it installs to the 2.6 installation.I have a Windows machine with Python 2.3, 2.6 a