WinXP: Games that don't need admin privileges?

I travel on business quite a lot, and have a laptop to take with me. Unfortunately, my office doesn’t trust me with admin privileges on this laptop (whether that is a good idea or not is up for debate). When I’m on my flights to and from the hotel, I’d like to play a game that’s light but fun.

I’ve installed Mozilla’s browser (and some extensions with game-like functions), and use it exclusively instead of the default (Nutscrape). I’ve installed Nethack which is a great little game. I’ve even tried putting Escape Velocity: Nova on, but it requires Quicktime, which requires… admin privileges! ARGH! So, when I’m tired of ASCII-based dungeon crawling, minesweeping, and solitaire, what do I install?

Bonus points if it’s silent (or doesn’t require sound to be on), has keyboard-based gameplay, and supports a “Save Game” function for when I’m in the middle of something pretty cool and we begin our final descent.