You'll have to buy something that's used of course. If you are buying online you have to be careful where you buy it, especially on ebay as there has been a trend of selling used laptops there without the Operating System (Windows), and the price looks suspiciously low.
Best laptops made in 2009, when Win7 came out are Dell and Samsung. As far as specs, you'll need to tell us what you are going to use the laptop for such as Gaming (not recommended), E-mail, social media, Graphics design (such as Auto-CAD), web research (google, bing), entertainment news, reading newsgroup feeds (RSS), or programming/web-design. There are hundreds of uses for computers, laptops especially, so that would be helpful. Post back how you intend to use it and which types of applications you are planning on using them for. Win7 laptops in decent shape can be had for $150-$500 or so. That should be in your price range. Use of graphics-intensive applications often requires both high-performance CPU chips and GPU chips (Graphics) and lots of RAM. 2 of these or all 3 of these will really drive the price up hundreds of dollars.
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