Help! The Chinese PinYin input under WinXP crashes...

Recently, when I tried to switch from English to Chinese PinYin input method, by hit left shift and alt keys, then the program I am running crashes. No matter whether I want to input Chinese in an internet browser, or note pad, or Word, the program crashes when I want to switch on Chinese input method.

So I can not input Chinese character.

I turned on the language bar and tried to switch to Chinese input through the language bar, then I got a message saying a file (shell.exe?) under system32 had problem...

Anyone could give me a clue?

I am using a Dell notebook with Windows XP.

Thanks in advance!