My requirement is to temporarily deactivate touch pad while I am using normal mouse since I'm rather familiar with the normal mouse to touch pad.
I consulted the Lenovo Thailand customer service and they told me to delete the PS/2 touch pad driver from MY COMPUTER\MANAGE\DEVICE MANAGER in order to use the normal mouse easily. Also they suggested to download Pointing Device (Synaptics) driver for Windows Vista 32-bit, 64-bid, XP - 3000 N200 (type 0687), V200. I did and installed onto my laptop. Then I uninstall PS/2 touch pad from MY COMPUTER\MANAGE\DEVICE MANAGER.
Then, I restart the notebook to make it effective.
Unfortunately, I found out that Lenovo is smart enough and trying to re-install the driver and ask me to do that. And my touch pad is not temporarily disabled. And I still have a problem with my touch pad even when I'm typing this mail.