Help with windows

ok so i have bought windows for my last 3 computers, im getting a windows 8 laptop i need for work and it has to have windows 7 on it for our inventory and book keeping programs, how would i go about installing windows without paying for another copy? the other keys are all in use right now, ive heard of daz loader but im not exactly sure on how it works, if anyone can post a guide and what ill need that would be great, i have a windows 7 iso from my last install on a hard drive already, its pro 64 bit

You either need to pirate it or a buy a new one.  There is really no legal way to get around paying for Windows.

not really worried about that, i just need a way to make windows 7 work on this laptop, how would one go about pirating it if one has an .iso already?

Windows has an official .iso on their website. Try using one of your previous keys on that; Windows rarely checks them, unless they are doing a sweep (rare.)

ahh, ill use one of my keys and see how it goes, i already have the iso from installing it on my gaming rig, so im just gonna use the same one