Windows Media Player in Windows 7 resize window to a standard size

this worked for me

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I think I found something of a workaround but maybe its not entirely what you want. If you open Windows Media Player (without opening a file) and switch to the Now Playing view, hold the ctrl button while resizing the window. Then exit and open a file. On my computer it will pop up at the same size I had just resized it to. 
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http://social.technet.microsoft.com/Forums/en-US/w7itpromedia/thread/fe9a9285-c2b1-4799-9be9-ae9cdc9cbadf
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