Installing Windows 7

I have a Dell Inspiron 1525 Laptop with Vista 32bit already installed. I only have 1 big partition (C:) where Windows, my apps and files are located. I've already backed up everything, burned the Win7 ISO on a DVD.

When I came on the hard drive screen during the install, it wouldn't let me format the C: partition. I assume that's because it was "already in use".

Right now, I am using Paragon Partition Manager to create a 50GB partition (E:) on which I'll probably install Win7 (I should have partitioned my HDD a long time ago but didn't do it out of laziness).

Now, what are my options for Windows 7? How can I format that C:? I really want a clean install of Windows 7. Can I format from DOS?

Thank you

How could I have missed that?

Thanks, guys. A lot. It's still installing, right now, though.

Hitting that rep button ASAP!

EDIT: After the Win7 install, will it be safe to partition my HDD (I am tired of backing up countless amounts of data) using a software like Partition Manager? I intended to partition before the W7 install...

From previous post:

After the Windows 7 install, will it be safe to partition my HDD (I am tired of backing up countless amounts of data) using a software like Partition Manager? I originally intended to partition before the Windows 7 install... but I just couldn't wait 1+ hour to install Windows 7!

Thanks, again.

And Merry Christmas and a Happy New Year to all you guys :)