Allocated Bootloader incorrectly

Greetings from Amsterdam. I have done something so stupid, that it is probabaly going to make you all fall about laughing. I am very new to Linux and I have on my older Fujitsu Seimens AMILO Li 3710 laptop a dual boot with Linux Mint and Linux Mint Debian Edition. I was exerimenting with Mangeia in a VM and liked it a lot. I have an old 200GB Lacie external hard drive that I used with my antiquated Mac. I reformated and partitioned it and then installed Mageia without any perceivable hitches.(Incidently, I'm extremely please with the result, even thought I am going to ask many questions). However it seems that I installed the Grub boot loader in the wrong location because I no longer see my Mint boot loader, only the Mangeia one. I have tried to boot with the Lacie disconnected and I still only get the Mangeia loader, so presumably I loaded it on the laptop. My question is going to be an obvious one. How do I rectify this? Or do I have to take the draconian approach and uninstall and start again. I feel very foolish. Please can someone help me in laguage that a newbie can understand. Many thanks.