I set up a RAID-0 server on a window machine using 4 harddisks. 100G each. Therefore the total size is 400G. Now, i removed all the data and
put the same set of disks on another linux Redhat machine using the same controler type. For some reason, I don't see each individual drive. All i see is a sdb having 400G.

To fix it, i connect individual drive to a external USB enclosure and create partition/format each one of them with ext3 (fdisk /dev/sdb, mkfs -t ext3 /dev/sdb1). When put it back on the controler, I still see the same 400G.

I think there might be some information about the previous RAID setup on the Harddrives. Is there a way to completely remove everything on the harddrives so that I can see each individual drive on the linux machine? Appreciate any help.!!!

Have you checked the second raid controller to see if there is an old setup on there?

How do I do that? This linux machine has mdadm install on it, but
i confirmed that RAID is not active (checked with cat /proc/mdstat )

What kind of raid controller is it? Can you give me a model number? If not, is it hardware of software?

It is SiI3124.
http://www.siliconimage.com/products/product.aspx?id=27
It comes with a tower for multiple disks.

I am not sure how to tell if it is software or hardware.
But I think it might have been a hardware RAID since it maintain the partition even i move from Window to Linux