Hi Shahzad Aslam,
I did some projects used RS232C (AT89C52 - PC) 3 years ago. No problem with it, I also used MSComm for interface (except that I used Delphi, but I think it is same with VB). Let me give you some advices :

Firstly, you should check your schematic because one often confuse RXD and TXD, male and female DB9. Moreover, the cable depends on DCE or DTE type is made correct. I recommend MAX232 for RS232C-TTL level.

Next, registers in AT89C52 must be initialized with correct value. Some of them are SP, SCON, TMOD, TH1, TL1 (if you use timer1). Whether you select interrupt or flag, you make the suitable source code.

Finally, you read document of MSComm from Microsoft (MSDN Library, ...). Then you change the value of some items.

For further information, you can contact me by email nguyentranminhnhat@yahoo.com
Bye