我用texmaker+miktex2.9，开很久以前编的档案时，出现
==============================================================================
It seems that this file cannot be correctly decoded with the default encoding
setting (UTF-8)
Use this encoding:
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它有一个选单给我选
可我不知以前的编码是什么？我试过UTF-8、Big5。中文显示都乱码。
我确定不是字型的问题。请问如何查编码？