Although I have installed many other distros, some of them 10's & 20's of times, I have never tried either that you mention, particularly Dreamlinux.
What I need to ask is what kind of boot loader options did the Dreamlinux installer give you? Most distros give you a choice between "MBR", "root partition", & "floppy". Xandros 4 automatically puts GRUB in the (1st sector of the) root partition regardless of where else you tell to install GRUB.
If Dreamlinux installed
any boot loader to the root partition, you can edit the DSL
/boot/grub/menu.lst to chainload it. To do this you/(we) need to know 2 things:
- What partition is Dreamlinux installed on?
- Did it install a boot loader there?
If this gets involved, a link to the Dreamlinux web site or other info. on the Web might be useful.
If you're interested, the official GRUB manual is here:
http://www.gnu.org/software/grub/manual/grub.html