Displaying Chinese characters
Unlike older versions of windows (XP and below), Windows 7 (and vista) already have language support built-in. This should be supported in all major browsers. If you do see strange characters instead of mandarin, make sure your encoding is set to “utf-8″, which includes both simplified and traditional.
Adding Chinese Input methods (IME)
Chinese input methods will allow you to use Pinyin or Zhuyin for typing Chinese characters. It also supports Traditional or simplified character sets.
I prefer the “Microsoft Pinyin New Experience Input St” under “Chinese simplified PRC”. This input type has fuzzy logic built-in which will show you a list of possible characters when you type in the pinyin and the tone number. It also supports both Traditional and Simplified characters.
Microsoft also recently released a Taiwan IME update for windows 7 and Vista, which includes full traditional character support. It can be found here