You must appear also on Google.com by default.
Your choices are:
1) Google.com only (both boxes unchecked)
2) Google.com and the Search Partner Network
3) Google.com and the Content Network
4) Google.com and Search and Content (both boxes checked)
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A couple of interesting threads about workarounds:
[webmasterworld.com...]
[webmasterworld.com...]
Tell us what you think. I'm inclined to try this approach with a narrow test.
patient2all
Your ads will be displayed in the websites you select. Start off a low daily budget and check each site if possible. If your keyword is generic, you will end up with lots of junk websites.