How to create a 6TB disk on Windows 2003 or Linux (32-bit CPU)?

In short - both Linux and Windows can do this for you.  You just have to configure the EMC device into a RAID 5 array large enough for you.  Then Windows or Linux can see the drive and format it.  NTFS can create file systems as large as 16 Exabtyes.  If I remember correctly, that's 16000 Terabytes (or possibly 16000000 Terabytes, don't remember if Pentabytes comes before or after Exabytes).

Linux can handle, as near as my research tells me, up to 16 Terabyte file systems.  Possibly larger, but I couldn't find information on that.  It does depend on the file system used and configuring your kernel correctly.

Though the following article discusses Windows XP, the description is for NTFS, which is the key to your question for the Windows portion:
http://www.microsoft.com/resources/documentation/Windows/XP/all/reskit/en-us/Default.asp?url=/resources/documentation/Windows/XP/all/reskit/en-us/prkc_fil_tdrn.asp

You may also want to have a look at this:
http://www.digit-life.com/articles/ntfs/

And finally (for NTFS) The maximum size of an NTFS partition is 16 exabytes. This is stated under "Volume Size" Roughly half way down the page on this web site:
http://www.microsoft.com/technet/prodtechnol/winntas/tips/techrep/filesyst.mspx

For Linux:
You might want to have a read at this:
http://www.suse.de/~aj/linux_lfs.html

Also,
http://www.jetico.com/linux/bcrypt-help/l_requi.htm

leew - those figures are max. theoretical file system limits, but Windows cannot format and use such volumes.

andyalder - i thought to do something like this - the question is - which software?

Don't think you need Veritas Volume Manager, once you have the three 2GB disks then Disk Administrator will let you stripe them or make a volume set. If they are three different pysical disks then use a volume set, if they are on three different sets of spindles then stripe them. A stripe RAID 0 set on a single set of disks leads to long seeks for what should be contiguous data.

Thanks, that's very useful!