Where I am, there are large datacenters that still use mid 1970s mainframes. Also, for some mission-critical applications DOS is still used as a kernel, again due to its maturity and lack of bugs (count how many "fixes" have been released for XP, compared with any of the earlier OSs. If I remember correctly, DOS 3.30 never had *any* fixes issued after its release.) Maybe stability, but definitely not speed or compatibility.Compatibility has not improved, for example the XP DOS emulator lacks many features and its speed is slow and intermittent. Setting ntvdm's priority to High or Realtime improves the performance, but the rest of the system becomes almost unresponsive. Speed has definitely not improved. All that's gotten faster is the hardware, not the software. The software continues to become less efficient. A look at the system requirements for XP vs 2K or any of the earlier OSs clearly shows this. More CPU and RAM are required for the newer OS.