Still love dos games, and want to use it on windows vista. Then download dosbox from here, http://www.dosbox.com/
Follow step by step guide,
1. After installation run dosbox, a command prompt will appear.
2. mount the folder which contain dos game
Z:\>MOUNT C C:\OLDGAMES
If games are in cd rom then
Z:\>MOUNT D D:\ -t cdrom
3. now change the drive
4. Change the direct where your favorite game is present, let say action games, in folder called "Action"
C:\> cd action
5. Run game
Ps: And you can find your favor dos games from here, www.dosgames.com