As you have not apparently used the OS since reinstall, it would be best to do it all again.
Bott up with the DVD.
When you get to the appropriate screen, on theWhich type of installation do you want? , click Custom.
It will then ask, Where do you want to install Windows? , click Drive options (advanced).
Click the partition that you want to install to.
Click the formatting option you want to perform.
Follow the instructions.
When it has finished formatting, click Next.
The partition will now be clean for your new installation.
Any other partitions can be reformatted when you are
back in the OS