hey
After quickly looking over the
teamxbox.com VDigi Electronics Enhanced VD-Z3 Review, I think it would be a nice VGA Box to get

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I thought I'd quote something I think is useful to know from that review.
edit
Hmm, I'm not sure now... I just read that it may not support all monitors or something? maybe it's todo with what resolutions your monitor supports? See
HERE. Hmm, what region Nintendo Wii do you have? If you have a PAL system, then your monitor may not support it? as I think for a PAL system the resolution would be 720x576 or 704x576. But if you have a NTSC system, then I think it would work on your monitor, as for a NTSC system the resolution would be 640x480

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But yea, I think your monitor only supports resolutions of... 1024x768, 1152x870, 1152x900, 1280x1024, 640x480, 720x400, 800x600, 832x624, and 640x350.
cyas