Maybe Portable Old Games?

There is a brilliant site called Abandonia. This site contains famous and classic games that were made ages ago (back in my time ^_^) and are absolutely free.

Some are not, but you will know about them when you find no link to that game to download.

Anyway... most of these games require DosBOX to play them, but a couple of them are compatible to play on XP. Some games like MDK and Turok are available to play.

Now I am not completely sure if they are portable or not, but I am quite sure they are.

Anyway, have fun with them, and look out for the XP logo on the page.

www.abandonia.com