How do I burn my windows 7 file into a cd?

Download a perfectly legal ISO copy of seven. link here. I should get paid for this.

http://www.mydigitallife.info/download-windows-7-iso-official-32-bit-and-64-bit-direct-download-links/

You will need a program like power ISO to make it bootable, but you will need to activate it with your original key ok? and it has to be the same version of 7 ok?

You can't legally. You do not own the license to transfer the Win 7 copy from the laptop to the new system, and the OEM which was set up for a laptop shouldn't work with the new configuration which is a desktop, windows OEM licensing will automatically detect upgrades, if the upgrades are too dramatic they will lock down the OS so it can't be used without a license release by Microsoft and they will know you are trying to transfer the license from a laptop build to a desktop build.