if you have two or more partitions, i would keep it simple, for example:
- drive c is only for windows and for necessary updates/driver software/office/itunes for example...
- drive d is for the rest... not so necessary (system) programs/games/photos/videos etc.
Btw. do you have a hidden system partition from where you can install windows back? rather than giving a command "format c:", i suppose you are using the system restore disk and partition to do so called "factory defaults/reset"? this is very simple way to restore the computer back to its original state (you probably can choose that only windows partition is formatted and others arent), but then lots of updates and many hours to install them all. (this is suitable for a person who is not familiar with the idea 'how to install the os to the empty computer')
if you are formatting partitions (rather than doing factory defaults/reset), before doing anything, better to check that the disk, which you are using to install windows back, is bootable and working in the first place. and can be used for installing windows in the first place too. possible serial/activation code is on the table too. this is the most problematic formatting/installing because you have to know what drivers you need - windows may have some general drivers to get the computer working but then you need probably to install almost all (specific from manufacturer) drivers manually. i usually have downloaded all huge updates (e.g. windows service packs/graphic drivers...) beforehand to make it easier and faster to install them... but not knowing better which windows and how you are going to install windows back, it is up to you which you need to do or prefer... also that the boot order (in bios) is right. you cant boot from the dvd, if the computer tries to boot only from the harddisk. (this option isnt suitable for a person, who dont know 'what to do next after having an empty computer in front')