Originally Posted by senorian
So if I already have Windows 7 installed (in a 100gig partition of a 1t hdd) how do I modify the windows booting process so that I can go on to create many additional partitions that will be used for linux distros?
You may want to view partitioning and booting separately.
You can have a max of three primary partitions plus one extended partition, with many logical partitions inside the extended partition.
Linux doesn't care whether its partitions are primary or logical.
There are many different ways to set up multi-boot:
The older DOS/Windows MBR code (and I think the new as well, but I'm not sure) is a simple routine that chain loads the boot code from the boot sector of the active primary partition. If you keep that MBR code (which is not the common choice) then your boot up sequence must always go through the boot sector of the active primary partition. That could be the Windows partition or (very unusual but possible setup) it could be a reason to make a Linux partition active-primary.
If the Windows loader is loaded from the active primary partition, I think it has an option to chain load to a boot sector copy in a file. I've seen that documented many places for XP. I'm not sure of details for 7. You install the first sector of GRUB or GRUB2 in the partition boot sector instead of in the MBR. You use DD in Linux (maybe in a liveCD) to copy that boot sector to a file in the Windows partition. You edit the Windows loader menu to offer a choice to chain load using that file.
The more common approach is to install Linux after installing Windows. Put Linux in either a primary or logical partition (it doesn't matter). Install Grub or Grub2 with its first sector in the MBR, overwriting the code that chain loads the active primary partition with code that loads the rest of Grub from the specified partition (that does not need to be primary). Then in the Grub menu, you put a choice for Windows that chain loads the active primary partition (or chain loads any specified primary partition and makes it temporarily active).
One copy of Grub or Grub2 can directly load many different installs of Linux, but sometimes you may need or prefer to have a menu choice to chain load to a partition boot sector (does not need to be primary) to load a different version of Grub or Grub2 (or other boot manager) to load other distributions.