Do you use XP Professional Edition? If so, just add traditional Chinese as an additional input locale.
Go to Control Panel, select Regional Options, select the General tab.
In the box for the language settings for the system, scroll down to find Traditional Chinese and tick the box. Then tick Apply.
Then select the input locales tab.
Tick the box for "enable indicator on taskbar".
Under Input language, click Add. Under input locale box, select from the drop-down list of languages Chinese (Taiwan). Then in the keyboard layout/IME box, select your input method, such as Changjie, Quick or Phonetic. Click OK.
This may require a restart for the changes to take effect. Next time you start, there should be an icon which reads "EN". When you need to switch to a different language, just click the icon, you should see a list of other input methods. Select the input method, and you'll be able to write in the new language.