i personally believe that it chooses MBR per default.
Now the things is it doesn't hurt if you enable to configure the advanced options and then make sure that MBR is selected (probably even click over to boot from boot partition and then back to MBR lol) - that way you make sure it does it the right way.
I just got Mandrake 9.1 on my other system installed, since I've read several threads about Mandrake being pretty good. For some reason it runs faster on my older system - actually thinking of setting it up on my main system as well...however, I also read some bad things about that distros.
here take a look:
We'll see how things work out hehe..