Okay, since you already have the images on a USB drive this will be a fairly simple procedure. The *only* thing that you may have to do after restoring everything is to ensure that your data volume gets the right drive letter (you can assign this after you boot the restored OS volume, if the correct drive letter is not already set).
Here are the steps you should perform:
0) [UPDATE] I forgot to mention that if you are restoring to another machine you must use HIR, and for Desktop and Server edition, HIR will only function on image files which contain an OS on which ShadowProtect Desktop or Server Edition is already installed. In other words, you have to have installed ShadowProtect and THEN take your image of the OS volume before you can use that image for an HIR restore to a different machine. IT Edition has no such limitation. IT will perform HIR against an OS volume that does not contain an installation of ShadowProtect.
1) Boot the IT Edition CD. I suggest that for your particular situation you boot the "Legacy" (Windows Server 2003-based WinPE) environment rather than the "Recommended" (Windows Vista-based WinPE) environment.
2) In the Disk Map tab, right-click and select the option to set the Partitioning Policy. Specify a policy which aligns the START of any newly-creation partition to the TRACK boundary, and aligns the END of any newly-created partition to the SECTOR boundary (these are the defaults in the new 3.1 environment which will be posted for download, as I understand it, some time this weekend).
3) Restore the OS image to the start of the new machine's 120GB drive. In the restore wizard, you'll need to specify the disk to which you intend to restore the image. In your case, you say the disk is not partitioned, so in the restore wizard on the disk list for the destination of the restore, right click on the disk in the disk list to which you wish to restore (the 120GB disk) and select the context menu item to create an exact-fit partition. Or create a larger partition if you like. ALSO in this same restore wizard, make sure that you check the box for HIR, as you are restoring to new hardware. HIR runs after the restore has completed and if necessary it will prompt you to provide it with storage controller drivers for the storage controller that's controlling the OS disk. It's generally best to have this driver available in advance. This driver is the same one you'd find on the F6-windows-install floppy (the one with the txtsetup.oem file). I prefer to simply place this driver on a USB drive and then in the HIR Advanced Options I specify the path to the USB drive so that HIR will use that driver rather than try to find one on its own. [UPDATE]: In HIR Advanced Options do NOT check either of the checkboxes (the domain controller checkbox, or the clear-config checkbox). One thing to note - when restoring Windows 2003, it's theoretically best to perform an HIR operation using the Legacy (windows 2003-winpe) environment, rather than the recommended (vista-winpe) environment. When using a USB device with the Legacy environment, you need to make sure that any attached USB disks/devices are plugged in and powered on (if they have external power) before booting the Legacy environment as the Legacy environment can't dynamically discover such devices (the recommended environment can). Also, when restoring the OS volume I suggest you check the options to restore the disk signature, hidden track sectors, and the saved MBR from the image, and check the box to set the partition as an active partition (this will be grayed out if the partition is already active). After completing the HIR restore of the OS volume, you will need to restore the data volume (there is no need to use HIR when restoring a data volume) to the 250GB disk. The procedure is similar to restoring the OS, but without the need to use HIR, and you do not need to check any of the boxes for MBR/hidden-track/disk-signature restore (they can all be left unchecked). Make sure that you mark the partition.
4) Reboot and boot from the hard disk (from your newly restored OS partition on your new machine. WARNING: If this SBS 2003 machine is a domain controller then on this first boot you must follow the procedure out lined in this white paper in order to properly rebind your NIC. It doesn't hurt to follow the instructions in this white paper for any HIR restore, really.
5) Reassign the drive letter of your data volume if it's not already the correct drive letter.
That's about it.
Some other white papers that you may find helpful are:
http://forum.storagecraft.com/Community/files/folders/supportwhitepapers/entry315.aspx
http://forum.storagecraft.com/Community/files/folders/supportwhitepapers/entry314.aspx