Presumably you're creating .tib "image" files with Acronis? That being the case, you would boot the PC with the Acronis CD and use the option to Restore an image file from the external drive. The procedure is no different from restoring an image when the C drive is messed up, or you want to get rid of some software that doesn't do what you require and revert to the previous state (which I do regularly!). The only difference is that you need to run Acronis from the CD instead of from the installation in Windows.
The new drive that you're restoring to *doesn't* need to be partitioned and formatted; Acronis puts in the existing partition, formatting and data.
If you got Acronis as a download and don't have the CD, you need to use the option to "Create Bootable Rescue Media".