There's also a way to run many older AGS games using new development version of engine. It now allows to run games from v. 2.5 and up, and you may select Direct3D renderer for them (there might be still a problem with certain plugins, that require DirectDraw), as well as scaling filters.
Not all versions are fully compatible, but I know that numerous old games were successfully tested.
You may get the preliminary release here:http://www.mediafire.com/?spm2y64et0r2dfz
Unpack the archive, then copy "acwin.exe" file to your game's directory.
To start the game - run acwin.exe (NOT game exe).
You won't be able to use winsetup.exe to set new settings, because winsetup.exe will run original game's setup. To configure game new way you should run acwin.exe with "--setup" parameter from command line.
If you don't know how to use command line in Windows, just download this batch file, copy it to game's directory too, and run anytime you want to change game settings:http://www.mediafire.com/view/?66373m22i8pa6b8
Please tell, if there are any problems.
NOTE: I should underline again, this unfortunately won't work if the game uses plugin, that requires DirectDraw (meaning, there will be no difference).
EDIT: explained how to run setup having acwin.exe.