Partimage is only available for linux. If you do not have linux installed on your computer, you can use it by booting a system rescue disk. If you already have linux installed on your system, it is recommended to install partimage using the package management system that comes with your linux distribution.
You can also download and compile partimage from sources but it requires more effort and there several libraries will be required.
Once you have downloaded partimage-x.y.z.tar.bz2, you must extract the archive and compile it:
tar xfjp partimage-x.y.z.tar.bz2
./configure --prefix=/usr && make && make install