I've just bought Photoshop but I'm unable to install on my laptop. I use Windows 10. I have Creative Cloud installed on there already but I only subscribe to Adobe Illustrator (under a different email)
You wouldn't want to subscribe under two different emails, surely? You can only be signed in to one account at a time, so you would be able to run Illustrator OR Photoshop, you'd have to sign out of one account, and sign in to the other account.
Anyway, what do you mean by "unable to install", please? What messages do you get?
I'd also suggest you don't have 2 Adobe products installled on the same computer that are associated to different accounts (different email). Confirm if this is the case. How are you installing Photoshop?