I've been considering trying out win 10 again..I believe I can dual boot them..What I have is two 1 TB hard drives first one has mainly the Win 7 OS on it..and one is all my sims,wargames ETC..I have easily over 500 GB free on each,,,What I have is an install cd burnt back during the free period..I've read I have to get a setup install from MS or buy a win 10 CD..Can I use the cd I have ?? I think I should free up some GB on either drive which I'm comfortable with and set up Win 10 to be able to give it a good test as to what games run and what don't....Getting confused about how to proceed..I would appreciate any advice about what path to take..I did try win 10 at first and a few older things didn't work rolled back to Win 7 and had a time getting it all correct again...Thanks for any advice

I would go get the latest version https://www.microsoft.com/en-gb/software-download/windows10 otherwise you may run into trouble. Last week I tried to do a refresh install using a slightly older Win 10 ISO and it wouldn't let me.

Just create a Win 10 USB installation,I find that much easier (besides my desktop doesn't have a CD drive).

That looks good but I have to buy a license,,I'm OK with that after I test it to make sure I want it for good.Eventually I hope to have a win 10/7 setup with Win 10 as primary and keep Win 7 for older sims/war games compatibility..When it was free lots of older stuff refused to run..and some just ran crappy

Do you have to buy a license? I thought Win10 sent some info regarding your system to some server somewhere.... I've reinstalled Win10 a good number of times on my sim rig and a couple of times on my son's computer and never had to enter a license code and Win10 recognizes the system once installed. Push comes to shove, I have my Win7 licenses that I can give when I ring Windows Support. I tried to get my license keys before but I ended up with a generic key and when I rang Win Support, I was told that the generic key is given out to those that upgraded during the free period... the key is then compared to the known hardware configurations and is validated that way.

I would suggest using Win10 Anniversary Edition. Seems like the Creator's Update had a few bugs when it was released. Found out the hard way when some of my hardware won't work under Win10CU when they were working fine under Win10AE.

You said you are considering trying Win 10 again so at one point you must have had it installed. If that is so and you still have the same machine then I'm pretty sure its hardware I.D will be logged on Microsoft's servers as -Ice pointed out.

If you create the USB media, when it asks you for the licence key just click 'I don't have one' and continue. Hopefully when the install is finished you will find that Windows is activated.

Yes I installed it twice before dropping it,,Unfortunately both my hard drives,,video card,,etc are upgrades from then...I probably can install win 10 using my win 7 oem key that came with the machine...but what I'm trying to set up is a dual boot win 7 and win 10 & for older games and 10 to get used to it and really see what it is like..My understanding is you can't dual boot from the free edition of Win 10 and Win 7..I've been messing with Windows since 3.1 a couple versions I skipped like Windows ME..I'd like to be able to run my older games and still learn about Win 10 because I figure when I need a new machine it will probably have Win 10..I quit building my own machine years ago and bought this HP factory rolled rig and just bumped it up a bit...Video,,Memory..P.S...I figure if a dual boot won't work I'll grab a Win 7 cd off Amazon..I have My HP OEM cd's but they won't work on a different machine

If Win10 is just a test to see what it's like and to see if your games will work with it, my sincere suggestion is to either buy a spare HDD or move stuff around so you have a spare HDD. Unplug all your other drives, plug in the spare HDD, and install Win10 to that one. Use it for a few days, test what you want to test, and see how it feels. If you don't like it, you have a spare HDD. Saves from having to do a dual boot and less cleanup to do should you dislike Win10.

I'm not sure if you can have Win7 and Win10 under the same hardware... you probably can but if Windows servers detect multiple boots of Win7 then Win10 and so on, it may clamp down on your key... from what I understand, it uses your Win7 key to give you a free Win10 key and you can jump TO Win10 or BACK to Win7 but I suspect there's a sensible limit to this to-and-fro'ing, so unless you have a totally different Win10 key, I would suggest play it safe and just try out Win10 for a few days then decide.

-ICE that seems to be the best way for me to proceed..I do have separate 1 TB HD's C:\Has my OS on it and it wouldn't be very hard to slip my games off of D: and throw 10 on to that ,,The machine sits in a place where it's very easy to unplug the SATA cable fro either drive,,Seems like a simple solution to some thing I was complicating..Thanks for solid advice

What are you worried about not working on 10 that runs on 7?
IMO, back up your game installations.
Install 10. If you've changed some hardware, it might not even matter. No one is certain what the combination of changes are that trigger an alert, but a hard drive and graphics card aren't that big of a deal. When you get into cpu/mobo, that's when I've seen it triggered. Even then you're given an activation phone number...it's automated...and you just do it that way. When they ask how many machines your OS is on, say 1.
Reinstall your games, test away.

Even if you decide to dual boot, it's usually advisable to have the newest OS on first.

Did you run the compatibilty advisor? It probably won't cover all games, but might answer some questions.
https://www.microsoft.com/en-us/download/details.aspx?id=20