If you buy English, they'll let you install English.
Chinese for Chinese.
Not Chinese -> English, as the pricing is different.
http://www.microsoft.com/downloads/deta ... layLang=en
(Only for Vista Business and Ultimate)
“Q. Can I downgrade my OEM version of Microsoft Windows Vista Business to Windows XP Professional?
A. Yes. OEM Downgrade Rights for desktop operating systems apply to Windows Vista Business & Vista Ultimate as stated in the License Terms. Please note, OEM downgrade versions of Windows Vista Business and Vista Ultimate are limited to Microsoft Windows XP Professional (including Tablet PC Edition & x64 Edition). End users can use the following media for their downgrade: Volume Licensing media (provided the end user has a Volume Licensing agreement), Retail (FPP), or System Builder hologram CD (provided the software is acquired in accordance with the Microsoft OEM System Builder License). Use of the downgraded operating system is governed by the Windows Vista Business License Terms, and the end user cannot use both the downgrade operating system and Windows Vista Business. There are no downgrade rights granted for Microsoft Windows Vista Home Basic or Home Premium.
Be prepared for hassle when you try it, but it is possible.
https://partner.microsoft.com/Malaysia/40042969
Here's the procedure incase the page is changed:
1.
Install the Machine with XP PRO Media and get any valid XP Product Key.
2.
After finishing the installation, there will be 2 options for you to pick for the Windows Activation. Activate online or activate through Phone Call. Pick activate through Phone Call.
3.
The system will show a series of Installation ID for activation.
4.
Send an email to
SEAPART@microsoft.com, and include all the information below:
1.
XP PRO Product Key and COA installed to the machine
2.
Vista Business/Ultimate Product Key and COA if possible
3.
XP Installation ID that shown in the system
4.
Customer information
5.
Microsoft will verify the information and respond within 24 hours. (Common case is about 5-6 hours)
6.
You will received an email from SEAPA, with the activation key. Key in the activation key.
I don't know how valid that email is since it's off the Malaysia partner page. But at least it's a starting point.