Buying new motherboard do I need to buy Windows 7 again?

[Legault]

I've been getting ready to buy a new motherboard since I bought a processor that isn't compatible with my current one. The thing is the computer I'm upgrading is store bought and I have an OEM version of Windows (No disc). Do I need to buy another copy of the operating system to use my new motherboard and processor? Most information I've seen would suggest so but I have no idea what to do. I'll be using the same HDD. Thanks in advance for any answers and if you need any information about the parts I will reply.
Edit: Oh, and if I do need a new copy of Windows 7, are there any copies I can buy for less than $50?

 

[nodsterr]

hell no, you can always activate over the phone and get angry with them and they will do it. Sometimes it just activates with no problem at all. As far as getting your key if you dont have it download belarc and it will find it for you.

 

[Calnin]

If you're using your old hard drive, you don't need to install w7 from what I've done. Just make sure to remove old drivers and install new ones.

 

[VP27]

OEM will usually not work if you switch motherboards, If you call Windows there is a slight possibility that they will reactivate if you complain and say this should be labelled better that this happens. It wont always work though so be prepared for that