There are language packs that can be installed using dism. Usually done by installing the language pack into install.wim,boot.wim and winre.wim. The packs come as lp.cab files.
How to integrate all language packs into Windows 7 | Hass - IT Consulting
It is possible to change language after installing the OS, by booting to pe and installing lang pack using dism, then set the lang defaults
dism /image:<path-to-os> /Set-SKUIntlDefaults:it-IT
Hunting language pack .cab files which are officially only offered to Microsoft's OEM partners is totally unnecessary, as well as is adding them with DISM.
You can simply install Windows 7 Ultimate or Enterprise edition on a technician machine and boot it to Audit Mode by pressing SHIFT + ALT + F3 after installation is done and OOBE starts:
In Audit Mode simply install language packs normally, then Sysprep and capture the image.
Microsoft has a very clear policy: language packs are available as optional updates for those running Ultimate or Enterprise. Not for any other edition. Installing language packs with any valid or invalid method to any edition than those officially supporting them (Ultimate and Enterprise) is a bad idea and might cause Windows either lose its activation or make it impossible to activate it in the first place. Using features not meant to your Windows edition with a hack or workaround is piracy as clearly as any other form of it.
An extract from almost six years old post, still valid and worth to read if trying to add language packs to any other editions than Ultimate and Enterprise:
Here some reading material regarding these language pack cracks:
My Digital Life said:
Windows 7 Validated As Non-Genuine on Unsupported Editions with MUI Language Pack Installed
After using hack to install language packs on non-supported editions of Windows 7, the Windows 7 operating system may be unsuccessful and validated as non-genuine (in other words, pirated or counterfeit) when user is trying to install updates on Windows Update or download files from the Microsoft Download Center. Genuine Windows validation also fails and returns negative status when user validates on Genuine Microsoft Software site.
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It appears that Windows Activation Technologies (WAT) starts to taking into account feature sets that available on specific edition of Windows 7 operating system when determining the genuine status. In this case, the non-genuine status is returned when Multilingual User Interface (MUI) packs that provide additional display languages in the operating system are installed on Windows 7 Starter, Home Basic, Home Premium or Professional edition, all of which is Windows 7 editions that does not support installation of MUI language packs.
Full article:
Windows 7 Validated As Non-Genuine on Unsupported Editions with MUI Language Pack Installed » My Digital Life
Kari