I got mine for the price, but it DOES keep my components very cool, And no, the cheapest you could get windows 7 for is $100. The CPU already comes with a fan, so you don't have to worry about that unless you are planning on doing some serious overclocking. As you can see, in the build I made for you... I have also already included windows 7, so you will have everything you need to build and use your computer.
PS: If you DO plan on getting a better heatsink for overclocking, I suggest you get this one: Newegg.com - COOLER MASTER Hyper 212 Plus RR-B10-212P-G1 "Heatpipe Direct Contact" Long Life Sleeve 120mm CPU Cooler Compatible Intel Core i5 & Intel Core i7
When installing the hyper 212+, apply the thermal paste it comes with onto the CPU, then spread it gently all over the top of the CPU before applying the actual heatsink. HOWEVER, the fan the CPU comes with already has thermal paste on it, so you don't need to add thermal paste unless you are installing a seperate heatsink.
Here is a video on how to do so: