Thanks for the answers. Though non of them helps me.
I know that there is no DOS, but there IS cmd.exe that allows to run the programs.
Indeed, the fact is that NTVDM that is used to run DOS and 16-bit Windows programs still exist in 32-bit Windows 7.
All i need is to run it fullscreen. Strangely enuf, on another PC, with the same Windows 7 loaded, the program is working perfectly, with fullscreen. Surely there is something that has to be adjusted on my PC.
The difference is that the WDDM drivers introduced with Vista and later have no full-screen support, where the XP display drivers does. Note that XP display drivers, however, has no support for any version of DirectX beyond 9 or Aero/DWM.