I am wondering does it matter if you delete or format C drive when reinstalling Windows 7? I usually just format the drive but i am curious is it necessary first to delete and then format C drive?
Delete what? Partitions? Folders? Files?
For a clean install, the standard method is to boot from the installation media and delete all partitions when you come to the "where do you want to install Windows" screen.
Windows will then automatically make and format the necessary partitions in the next steps in the install. You don't have to specifically ask it to format anything.
If you want to, you COULD format the C drive before beginning, but it isn't necessary under normal circumstances. Just delete partitions within the new install.
I assume you saw the screen show below and chose "drive options, advanced"?
Earlier on, did you choose "custom" install?
It's been a while since I've done it, but I think the "drive options, advanced" choice leads to the screen in your post.
Choose delete, not format. For each of those partitions.
For a clean install, you want to get rid of all partitions and let Windows make new ones.
If you want, you can instead use Diskpart to make one single partition and then tell Windows to use that single new partition as the destination---rather than letting Window make the partitions. If you did that, you'd end up with just C, and no System Reserved. That's how I do it, but it's not standard. The standard method results in a System Reserved.
More than one way to skin a cat.
There is no need to delete (or even format) any partition to reinstall Windows. If you just will be recreating the same structure as before, deleting and recreating partitions has no practical effect, so I wont bother. But neither does any harm to do it.
The same with formating the drive. Doing so will ensure that the drive is totally clean and only contains Windows after the process, but skipping the reformat keeps every single file in its place, in addition to install a new copy of Windows. How do you do it depends on what are you trying to achieve and how much "cleanness" do you want in the new system.
While usually recommended that you must delete everything in the hard disk before beginning, it's not actually necessary. It's more a double-checking to make sure you're back at a brand new install.
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