INT 21 - LANtastic v3+ - GET USERNAME FROM ACCOUNT FILE                         
	AX = 5FB2h
	BX = username entry index (0 for first)
	DS:SI -> 16-byte buffer for username
	ES:DI -> ASCIZA NUL-terminated ASCII string.	The ASCIZ string "ABC" consists of the four bytes 41h, 42h, 43h, and 00h.  Unless otherwise specified, maximum lengths given in the interrupt list do not include the terminating NUL. server name in form "\\machine"
Return: CF clear if successful
	CF set on error
	    AX = error code
	BX = next queue entry index
SeeAlso: AX=5FB0h