On the last night of Win 8 Pro being available at $40, I got a question about changing the operating system language of a computer fitted with Chinese Win 8 PRC to English. Unfortunately I had done my own last-minute purchase and download of Win 8 (in English), here in China, and had gone to bed. I'm so sorry about this because I got a lot of help at this forum, on the same night.
My computers were bought mostly outside of China. The reason was that it's quite difficult to turn Win 7 PRC or Win 8 PRC pre-installed on a locally bought PC to English. In China, most new PC's are sold with the basic version (not the Professional or Ultimate versions) of Windows pre-installed. This means you have a big problem. You can't change the O/S language to English. Windows 8 PRC can be superficially set to English. But Chinese will pop up at every corner when using the machine. The "core" O/S language remains Chinese.
"English-speaking" PC's with Windows as O/S cost about 20% less in Hong Kong than in the PRC, for the same computer model. A second-class overnight return train ticket between Shanghai and Hong Kong costs around $200. An English Windows DVD in a box might cost you around $500 in China. Through shops in the Computer "Markets" (Plaza's, Bazaars) you can buy a genuine English Win 7 OEM version for around $150-$200.
The best thing is to travel to Hong Kong to buy your new computer, or -- for much the same money -- get someone to install a Win 7 or Win 8 OEM English version of the O/S in China itself. When I last inquired, Win 8 OEM on disks was not available yet.
The question remains what happens when you buy and start to download an English version of Win 8 on a new machine fitted with Win 8 PRC, inside China or elsewhere. If this is possible, it would be one more way, apart from going to Hong Kong or going to your local Chinese "Market" for an OEM disk, to pay a premium of $200. Another mystery question is whether the Product Key of your Win 8 PRC will activate an English version of the O/S if you could somehow get hold of that. I'm curious what would happen if you applied you Win 8 PRC product key to a cracked English version of Win 8, something that will certainly be tried here in China.
Who knows the answers to these questions?