Hi Shahzad;
What is your Xtal frequency? The baudrate depends on Xtal freq. For details of initialization read the "MCS 51 MICROCONTROLLER FAMILY USER'S MANUAL" that is in the links. A sample/simple program may be written as:
ORG 0000H
JMP START

START:
MOV TMOD,#20H ; USE TIMER 1 FOR BAUD RATE GENERATION
MOV SCON,#50H ;
MOV TH1,#0FDH ; 1 N 8 9600 BAUD CONFIG. FOR 11.0592 MHZ XTAL
SETB TR1 ; START TIMER

MAIN: MOV DPTR,#MSG ; MESSAGE THAT WILL BE SENT
MOV R7,#4 ; LENGTH OF MESSAGE
LOOP: CLR A
MOVC A,@A+DPTR ; GET FIRST BYTE
MOV SBUF,A ;
JNB TI,$ ; WAIT FOR TRANSMISION
CLR TI
INC DPTR ; POINT TO THE NEXT BYTE
DJNZ R7,LOOP
CALL DELAY ; WAIT
JMP MAIN

MSG: DB 'TEST' ; MESSAGE

DELAY: MOV R6,#250
DELA: MOV R5,#250
DELB: NOP
NOP
DJNZ R5,DELB
DJNZ R6,DELA
RET
END

Also I recomend you to test with Hyper Term instead of your VB program. To be able to find the problem (AT89? or your VB program?)
Regards.
Ertan