newbie question

so i'm trying to fix a corrupted MBR on a Drive...
I have :
Drive 3
Partition 1 (OxDE - 39MiB)
Partition 2 (G:\ as NTFS - 9GiB)
Partition 3 (H:\ as NTFS - 457 GiB)

So which partition do I "Install the Windows Vista/7 bootloader"?????
The MBR isn't part of any partition. It's a fixed block at the start of the HDD before all of the partitions.
(The dropdown on that page is not part of the "Install Vista/7......" section. It's only for creating external media like flashdrives)
(told you I was a newbie)

History: My computer won't boot.... I removed the drive from my XPS 435 and used a drive docking station plugged into a laptop... I can access all my data....

One of my friends thought the MBR was corrupt....

So how do I repair the MBR??