I want to know what is in the 100mb System Partition of my drive, and if i could the windows installation CD to format/delete it.
It is a partition that windows creates for the Boot Configuration Data (BCD) and is also used by Bitlocker if you encrypt the HDD -- so you do not ant to mess with it or the system may stop booting -- As foscooter mentioned you can remove it if not using Bitlocker but need to follow certain steps to make sure it is removed properly or you may wind up reinstalling the OS.
reinstalling the OS is not a problem in fact thats what im trying to do but why is that part partitioned separate from the rest of the drive instead of just with the rest of it
Windows will create it if there is unpartitned space on any of the HDDs in the system -- to prevent it from being created reformat the HDD and manually create the partitions before running the installation (also best to only have the one HDD in the system while installing the OS or it will sometimes place that partition on a second HDD creating problems if you ever swap out a HDD !! ) - If the HDD is already partitioned it will just add that info to the system partition instead of creating a seperate partition but if there is free unpartitioned space it will create the 100MB reserve.
Main reason it creates it before the installation is so that those files can be located at the optimal position on the HDD and not wind up fragmented throughout the physical HDD so that the system will boot at the fastest possible speed since the files are concentrated in a specific place on the HDD.
IF for SSD
If you are re-installing the OS, You can delete it. Select custom install and on the page that asked where to install to, select advanced and delete ALL partitions (I always do this when reinstalling win 7 to an SSD). Then just select the Unpartition Space to install windows to - Windows 7 WILL recreate the 100 mb system partition.
The only time you want to mess with this guy, is if somehow a large file got stuck in there. You will find out quicky if you do an image file of C drive using windows Backup - You will get a out of space error. and SCRATCH your head as you have a bunch of space on "C" drive. Reason I know is, it happend to me, and it was a pain figuring it out and how to delete that file.