You can install Ghost onto any suitable platform then create a bootable WinPE image which can be written to optical media (for booting from a CD or DVD) or which can be written to a USB device and booted from there. This gives you the possibility of configuring a USB hard disk as a WinPE bootable device and thus writing the image to the USB disk before replacing the hard disk.
I think you are confusing the term "active" with the term "formatted". A partition that is bootable, but which does not have the "active" flag set, will not boot.
If you hope to image XP by cloning direct to another drive, and then hope that the replacement drive will boot, you need to check whether the cloning program rewrites the boot.ini unchanged or whether it realigns it with the target drive device number. The latter will definitely prevent a successful boot if the target is then re-homed as the primary drive, unless you edit the boot.ini.
I too have used Acronis to image "difficult" drives, and have always opted to use the external storage approach to hold the image, restoring it to a replacement drive on the same hardware port. This has always worked for me. However, I cannot recall any occasion when a disk to disk clone ever booted successfully for me, except in one instance many years ago where an IDE hard disk controller offered a hardware bit level cloning capability in its bios. YMMV