Shouldn't be difficult should it - done it many times before, but this time it's driving me bonkers

It's a Dell 7010 Ultra Small Form Factor Intel Core i3 3220 3.30Ghz, 4GB Ram, 320Gb Hdd with (OEM)Win 7 pre-loaded. HDD and CD are both SATA
What I'm trying to do is replace the disc with an SSD one. So, create a system image, create a system restore CD, physically replace the HDD with the SSD one, boot off the system restore CD, and load up the image to the new drive. How hard can it be

Well the first issue is this PC has only two SATA ports, one dedicated to the hard disc, the other to the CD - so nowhere to put the system image except on a network drive.
So I've generated a system image successfully across the network, swapped the drives, booted off the system restore CD , poined it at the image (which it sees) but it refuses to use it for restore

So I've attached a 1 TB USB drive to the system, generated another system image, but again it refuses to use it to restore

So I've installed the new disc in another PC that has more SATA ports, booted off the restore CD, but it won't load the image

Now there's nothing particularly important on the original drive except the operating system, so I thought if I did a clean install using one of my genuine Win7 professional 64 bit distribution CDs and use the Certificate of Authenticity number off the PC as it's definitely genuine I should end up good to go. Loads up fine, runs, but the COA won't authenticate - presumably it needs to be loaded from a Dell OEM version of Win 7 professional

... argh my head hurts
Current 'plan' is to pull the internal CD thus releasing it's SATA port, install an external CD reader via USB, and try and do a back up and restore internal to the PC - so USB CD reader on order !
... why do I hate PC's ...... I wonder
