That's why it won't let you format C: You can't format the drive you boot from or where Windows is running from.
You'll need a boot CD and since you have no install CD you won't be able to reinstall this OS.
As to your request, why not ask Dell? They will answer and then you know what to do next.
I'm trying to wipe the entire hard drive on my Dell PC that I got 5 years ago. This would involve wiping out both my E: (3Gb of space) and my C: (145Gb of space).
When my bios starts up I have the option of booting XP with the E: or the C:, but I can only boot from the E: because my C: is damaged. My C: is the system partition and E: is the boot partition. Both Win XP installations are from the same serial key. I don't have a CD with the Win XP setup on it, but I downloaded a Home/Professional SP2 version that I can run from within the E: (as it is my only stable drive). However, when I try to run the setup and format my C:, my system claims that there are important system files on the C: that are needed to complete the setup.
I have no system restore points to roll back to, in case you were wondering. Would I be able to use the Recovery Console from Win XP setup running from the E: to restore my C:? It doesn't make sense to me why I can't format/delete my C: partition if I'm running from the Win XP setup. Can I request a Win XP installation CD from Dell even though my warranty is surely expired? (They never sent me an installation CD in the first place).
Any suggestions, answers, questions are appreciated.