JSI Tip 6293. Windows XP will NOT run some DOS programs unless they have focus?

The Windows XP NTVDM (Virtual DOS Machine) has been enhanced to detect VESA (Video Electronics Standard Association) BIOS calls and automatically switch to full-screen mode. This is required because NTVDM does NOT emulate VESA BIOS functions, relying instead on the presence of VESA hardware and software, and on full access to the video hardware, without emulation, which is only available in full-screen mode.

If a DOS application makes a VESA BIOS call in Windowed mode and the application does NOT have focus, NTVDM waits for the window to have focus before making the switch to full-screen mode.