Windows Best offline game?

Arma 2 (Combined Operations), if your laptop is capable
Using the editor Arma 2 is endless...

 

I would caution against KOTOR unless you have very good luck or an XP install somewhere. Why? The game is horrifically unstable. It's performance is worse than SimCity 4. Mind you that's KOTOR 1. KOTOR 2 is a bit better. But not by much.

 

Offline games that I really like to play are :

Call of Duty 4 modern warfare ...is one of the my favorite game. Another latest game I just completed that Max payne 3

 

Freespace series, but you need sound and a numpad - and a good size mousepad!

 

GTA SA

 

P.S All the GTA games plus COD

 

Max Payne is not an offline game - it requires an Internet connection at start up to connect to that stupid Rockstar Social Club thing.

 

Touhou
Bastion
Recettear
Costume Quest
Amnesia The Dark Descent
Auditorium (or basically any puzzle game...)
Stepmania (or basically any rhythm game...)
Braid
Super Meatboy (or basically any arcade style game...)
Half Life 1/2
Mirror's Edge
Knights of the Old Republic
Tower of Heaven (if you can find the download version)
Cave Story

I could keep going but I'm getting tired of typing ^^.