I got it starting up here with our cxgames 8 nightlies, we'll give a shot at supporting it. Other than the problem with the DX runtime install it is a fairly simple game, so the graphics and sound part shouldn't make too much troubles.
I think it doesn't need .NET, although Steam tries to install it. It does however need the very latest DirectX runtime.
Now the problem is that we install the DX runtime with winver=win2k, because otherwise it does not install some files that already exist on WinXP, like DirectPlay. However, the game needs some new runtime files that are not supported in Win2K, so we'd have to install it with winver=winxp.
So what you have to do is to go into the steamapps/common/the secret of monkey island.../directx/ folder. Then, run the dxsetup.exe there. It will run with winver=win2k. Then, open winecfg for the bottle, look up the dxsetup.exe profile from the list, and set it to use winxp. Then, run the installer again. After that the game should start up.
There's still a graphics bug, but that should be easy to fix.