Do not use the C run-time BIOS interface routines with Windows.
You can use the C run-time Interrupt 21h routines intdos, intdosx, and some of the _dos functions such as _dos_getdrive. You can also use the int86 and int86x routines to invoke interrupts other than Interrupt 21h. However, you should use interrupts with extreme caution and only if necessary.