Thanks Malaire, Harry et al for the input.

I tried the two codes but I still get the same error message.

mount: /dev/hda5 already mounted or /home/knoppix/hda5 busy

I find that knoppix is able to detect the removable usb drive(already mounted). However it can only read from the usb drive and not write to it and I find that I cannot change the read write permissions even from root using chmod. It tells me that the disk is only readable whereas I could do both read and write from windows.