Re: is it necessary to edit MBR for installation
First, you will have to delete that D partition because ubuntu can't install on ntfs. Just use windows Disk Management and delete it, leaving the space as unallocated (unpartitioned).
Personally I prefer the grub2 bootloader, instead of going the EasyBCD route. But the choice is yours. Horror stories are all around and forums exist for people to complain and ask for help, not to post when they are happy. So, don't pay too much attention to it.
Of course, you need to have at least a little bit of knowledge what are you doing, otherwise any OS can turn into horror, not only linux.
The bottom line is:
Option 1. If you have one hdd, it's very simple. Delete the D partition as mentioned, and if you don't want to do any custom partitioning just use the "along side win7" option and the installer will use the unallocated space you left, install grub2 to the MBR of the disk, and in 98% of cases, it simply works.
If you happen to be in those 2%, it's not the end of the world (yet). We can probably help you to get your computer up and running fast, just keep the ubuntu cd at hand since it allows you to boot in live mode (Try Ubuntu) even if the hdd doesn't boot.
Option 2. To leave windows bootloader on the MBR and use EasyBCD, you will have to delete the D partition also, but during the installation you have to use the manual method creating the partitions manually into that unallocated space. And select the bootloader grub2 to go to the ubuntu root partition. After that in windows use EasyBCD to add ubuntu entry to the windows bootloader.
So, for option 2 you have to do manual partitioning which sometimes has the risk to really mess up the hdd, if you are not used to it. Also, even if it works OK, later during grub2 updates it can break grub2 and you will have to reinstall grub2 to the partition boot sector. This can happen because grub2 doesn't fit on the partition boot sector so it leaves part of it's code on the root partition. During an update this code can move and the grub2 part on the partition boot sector will not be able to find it until you reinstall it.
I think option 1 is much better, and easier. And you? As always, the choice is all yours.
Ubuntu 12.04 LTS 64bit & Windows 7 Ultimate 64bit