Thanks alohadave and peter for your help.
Thanks also to a gentleman who PM me to inform me that this software can do this as well.
http://yuren88.myweb.hinet.net/file/PhotoCap422_EN.exe
This is apparently a Taiwanese made freeware. There is a English version available. I have just downloaded this a try it out. U just need to use the paint brush to paint the background with a greyscale brush and it works.
Thanks and consider this thread closed
Cheers!!