Good Steam games for old laptops

I can recommend Torchlight 2. I still play it. :)

Some low spec (I guess) that I liked and own. You mentioned disk space so these are mostly small size.

https://store.steampowered.com/app/474210/BUTCHER/
https://store.steampowered.com/bundle/3736/Turok_Bundle/
https://store.steampowered.com/app/434050/Duke_Nukem_3D_20th_Anniversary_World_Tour/
https://store.steampowered.com/app/2310/QUAKE/
https://store.steampowered.com/app/225160/Shadow_Warrior_Classic_Redux/
https://store.steampowered.com/app/238070/Shadow_Warrior_Classic_1997/
Free version ^
https://store.steampowered.com/app/9010/Return_to_Castle_Wolfenstein/
https://store.steampowered.com/app/1379630/RealRTCW/
With this mod ^
https://store.steampowered.com/app/219150/Hotline_Miami/
https://store.steampowered.com/app/274170/Hotline_Miami_2_Wrong_Number/
https://store.steampowered.com/app/306700/Iron_Fisticle/
https://store.steampowered.com/app/548680/Iron_Crypticle/
https://store.steampowered.com/app/491040/Bot_Vice/
https://store.steampowered.com/app/598730/Shakedown_Hawaii/
https://store.steampowered.com/app/600130/Valfaris/

Fallout 1 & 2

You can also use CanYouRunIt for lazy checking. :)

Since CrossCode and Torchlight 2 already mentioned;
Worms Armageddon
Plants vs Zombies
Ys I&II
Ys Origin
Prison Architect
Shadowrun Trilogy
Goetia
Mini Metro

Play any of the old classics, you can't go wrong with that. Whenever my computer breaks and I have to use an older one I always see it as an opportunity of playing older games that I always wanted to play.

If you like hack & slash action pretty much all the Ys games. At least up until Ys Seven they run on a potato. My recommended picks are

• Ys Origin
• Ys: The Oath in Felghana
  They're also super cheap on sale right now.

If you like strategy RPGS, I can recommend the Disgaea series starting with

• Disgaea 1
  The first couple ones are also dirt cheap right now.

When all I had was a low-end laptop, I really really enjoyed Railroad Tycoon 2 Platinum, Sid Meier's Pirates, and Civilization 3. In all likelihood I spent over 3000 hours in those games, on a computer than had a whole 512 MB of ram.

that's some real classic games.
Half-Life, Half-Life: Opposing Force, Half-Life: Blue Shift.
Heroes® of Might & Magic® III (one of my all time favorite game)

Sid Meier's Pirates!

https://store.steampowered.com/app/3920/Sid_Meiers_Pirates/

Best pirate game of all time. Currently on sale for under $3.

100% orange juice

if you have 30MBps internet download speed,you can also play via
http://play.Geforcenow.com or http://xbox.com/play Cloud Gaming services
you don't need a console or a powerful pc for use them but you will see games with recent powerful graphic,
my internet connection is around that and i play and finish many games with these services and i'm very happy about them.
They will enable you to see via streaming latest games as cyberpunk 2077 without need of powerful or recent pc,it's same if you connect via remote\teamviewer to a powerful pc of a friend and play with it.
Geforcenow is free with wait time and no raytracing or cost $9,99 with Raytracing and no wait time,
xbox cloud gaming you can get with $1 xbox game pass ultimate actual deal
and with this you will get also around 100 games to play for free,
included some of the latests and triple aaa + 3 games for the games with gold too,
that you can play until your subscribtion is active,
and if you don't care about achievements or long term play when the subscription finish you can just create a new account for re-enjoy the $1 deal, it's better if you subscribe to the service with a temporal\virtual one-time-use credit card or with a cc that enable you to Limit dayly purchases costs so when the month finish you will not be charged for "renew" , it's also better if additional to this you turn off the renew feature in account.microsoft.com .

Levelhead is pretty fun and it works on my 16 year old laptop 😂

One of my all time favourite games, Disciples 2.

https://store.steampowered.com/app/1640/Disciples_II_Galleans_Return/
https://store.steampowered.com/app/1630/Disciples_II_Rise_of_the_Elves/

Also "Nox". This game isnt on steam but you can find on gog.

I don't know if anyone already suggested this, but since your specs are so low and your hardware so old, you should install Windows 7 x64 for better performance and MUCH greater compatibility with older games.