Usually, when Ubuntu is installed second, the Ubuntu installer will overwrite the MBR with its own version of GRUB, and this GRUB will read the /boot/grub/menu.lst that resides in the Ubuntu partition.
Therefore, usually the Ubuntu partition will be the one "controlling" the boot process.
(And in general the last OS you install will control the boot process).
However, if you are concerned that this may not be the case for you, you could do this:
Boot into Linpus. Find the file called menu.lst. The path is probably /boot/grub/menu.lst,
but if not, try to find it with any search tool you like, or type
Now edit the menu.lst. (You'll need to be root.)
Go about 2/3 of the way down until you find a stanza that looks somewhat like this:
The title line is what shows up in the GRUB menu at boot time.
kernel /boot/vmlinuz-2.6.22-14-generic root=UUID=03a507ee-cdac-4bd9-b438-eccd616b66ed ro
You can change it to whatever you like without disturbing the boot process.
So change the title line to
save and exit. Reboot. Get to the GRUB menu. If you see "Linpus Controls the Boot Process" as one of the boot options, then post back and we can give you instructions on copying Linpus's menu.lst to the Ubuntu partition and redirecting GRUB to boot from the Ubuntu partition.
title Linpus Controls the Boot Process
If you don't see "Linpus Controls the Boot Process" in the GRUB menu, it means Ubuntu's menu.lst is already controlling the boot process, and you are free to delete Linpus.