In addition to Tripredacus comment:
replace the second line:
For the Enterprise version, assuming you are using KMS, you normally don't specify a product key at all, just remove the <ProductKey>ABCDE-FGHIJ-KLMNO-PQRST-UVWXY</ProductKey> section. If you are using MAK keys, you should use that one. The keys acts as a filter for the setup, so if the key is not correct you will get a "operating system missing" error.
As for the joindomain issue the answer looks quite ok at a first look, except for that you should not add computers to the computers container, it's only there for legacy reasons, use an OU...
Anyway. check the c:\Windows\Debug\Netsetup.log for info on why the domain join failed.
We don't have a KMS server set up. The image capture tool is ImageW.exe (included in LANDesk OS Deployment Suite) and it takes a sector based image of the pc. I'm thinking if I enter the key manually and activate windows and then take a capture it might work. I'll remove the product key from the XML file and try this.
Regarding joindomain, will point to an OU and check the NetSetup.log and write back.
Thanks for the advice.