Use the bootable live linux cd, knoppix. Two good reasons why:
1. Partimage is included on knoppix so there is nothing to install;
2. With partimage, the partitions that you image cannot be mounted when you image them. This means that if you install partimage on a running linux system it will not be able to image it. That's why everbody uses a boot cd with partimage.
Check out this link re partimage usage and other imaging options: