or check Google pinyin input tool out, http://tools.google.com/pinyin

Just use your Windows IME. http://www.microsoft.com/windows/ie/ie6/downloads/recommended/ime/default.mspx

personally i recommand 拼音加加 (http://dir.jjol.cn/Pyjj/) you can also download from http://www.crsky.com/soft/271.html if you like, you can use online IME: http://dict.cn/ime/ as well. ps: dict.cn is a great translation site.