Need ideas for old laptop usecase

I am gonna join mtech and I just bought a new laptop (Lenovo Ideapad Slim 3) because my 7 year old laptop( Hp pavilion i5) got slow and cant really support the software I will be using. I dont want to throw that laptop.
I need suggestions on how should I use it , using it as a second screen is one option , but are there any better ways to use it? I was also thinking of installing linux in that.
Should i reboot it and use the same microsoft login as my new laptop ? ( they have different outlook mail logins).

I dont play games on laptop , hence my purpose for second laptop is just work related