From your explanation, I would give '(hd1)' another try. Don't forget to run 'sudo update-grub' after finished editing. Also you may want to explore other option as well beside chainloader. The fact I am doing because my main OS is Fedora and I want to boot into Ubuntu once in a while via chainloader. If your main OS is Ubuntu/Mint with Grub2 which is more powerful, you can also configure Grub2 to autodetect other OSes via the os-prober as pointed by Don1500. However, for this os-prober to detect Fedora, your system need LVM2 package to be installed and the LVM to be preloaded by Grub2.
To install LVM2, use the Software Manager or synaptic or apt-get as usual. The package name is lvm2
To preload the lvm module, edit /etc/default/grub
to add this line to the end of the file:
Reboot. The next time you run os-prober
it should list other OSes on LVM (including Fedora).
Finally run "sudo update-grub" to add those new automatic entries into grub.cfg.
If you do this, you do no need the chainloader custom entries in 40_custom