Microsoft just released the MUI language packs language packs for the Windows 10 build 10061 x64. These language packs will allow you to apply a new display language to your operating system.
If you upgrade to Windows 10, the packages will appear in Windows Update or through the Control Panel in the Windows language tab.
However you may be interested in downloading a language pack so that you can use it when you need it from your hard drive, eg. to install it on multiple computers at once or if you don't want to download the huge files again after a restartinstallation of Windows.
Here is a huge list of direct connections for Windows 10 MUI language packs for iGuRu.gr readers.
At the moment, the company has not released the Greek package.
Stay tuned, as with the release of the Hellenic Package, you will find it first at iGuRu.gr.
Install a MUI Language CAB File in Windows 10, 8, and 7