i would install those games, make a new profile in each of them, and see where the saves go after exiting.
i think most of the games put them in the My Documents folder in Windows 7. do check both the My Documents folder, as well as maybe the My Games folder. Sometimes they can also be in the (usually) hidden AppData folder in your User folder - either in the Local or Local App folders, under the game company.
i don't imagine that most saved games can get very large in file size, so you can also use USB drives to carry them over between computers. when i usually finish a game, i will incorporate the Root save folder directory into my yearly backups, so i don't have to replay much of the game down the road.