That depends how "Chinese" you want to turn your system into.
If you simply wants to type Chinese, display Chinese, create a Microsoft Word document in Chinese, English Windows 7 is capable of doing that. You will need to add the Chinese keyboard in the Regional settings in the Control panel (there are many Chinese entry methods; so choose one that you are familar with). Once this is done, you will see an icon on the task bar that you can switch to different language keyboards. When you want to switch to typing Chinese, switch to keyboard to Chinese and you are set.
On the other hand, if you want change all the system dialog boxes, names of the programs, English "Start" to Chinese, etc., the best way to approach this is upgrade to Windows 7 Ultimate (you can get a Windows Anytime Upgrade for this), which you can use its language pack capabilities to turn almost all of the dialog boxes into Chinese.
