Self Encrypting Drive (SED), partition modification?

Question

I have been given a computer with a Win 7 on it and a Seagate ST500LT015 SED drive. I love the idea of have hardware based encryption eeven if having a TPM that does "whatever it wants" is kinda scary. But that's irrelevant to the question.

IT tells me that if I modify the partition of the drive (after unlocking) will be detected and lock the drive. After hours of research online I could not see one single notification of such behavior. Secondly, my understanding of the drive is that the 75Mo boot partition needs to remain untouched. If I'm not mistaken the order of the boot is as such : ON > BIOS detects drive > BIOS ask for MBR > HDD anwsers 75mo Boot partition > BIOS loads up the Mini OS > Credentials are tested against the key > If OK HDD is unlocked and the computer reboot > BIOS ask for MBR > HDD anwsers real encrypted MBR

In that case, the credential part never really sees the MBR and partitions right ?

Thus can I modify the partitions and MBR (to install linux for example ? )

Thanks