Windows XP is very good, because if you install with the East Asian Language, then you are able to type chinese with built-in IME (Input Method Editor).
And recently, introduced by my brother, Sogou Pinyin Input 搜狗拼音輸入法. Then I found that, there are other IMEs which are much better than XP built-in IME. And I also tried Goolge Pinyin Input 谷歌拼音輸入法, which is also very famous as Sogou Pinyin Input. If you like, you can try some other IMEs from here (very good, all are freeware).
FYI, both of Sogou Input and Google Input are using GB (simplified chinese) encoding, so you need to setup your XP to simplified chinese encoding first. So that there is no mojibake (亂碼).
Sogou Input and Google Input has a powerful input method, that is find the character stroke by stroke, the stroke input (筆畫輸入). You can find out more from here.
And I also compared both products, Sogou Input and Google Input. Then I prefer Sogou Input. Because Sogou’s stroke input is better than Google’s, because “豎” contains 勾 also (if you want to try, just type “u” for stroke input, then type “s” for 豎). But this is not the main reason. Main reason is that, during installation, Sogou is cleaner. It will not affect a lot on startup.