To delete partitions within Windows there must, obviously, be a working system on the C drive. Ordinarily, a second hard disk would be the one to be deleted/created but it could be on the same drive as the operating system. Go to Start, Administrative Tools, Computer Management and click Disk Management. Right click on the drive to be deleted. Firstly delete logical drives then extended partition and then primary partition.
To create partitions go to Disk Management, right click the drive and set up, firstly the primary partition, then the extended and n number of logical drives within the extended partition. They can all then be formatted by right clicking them. The primary partition should also be set to active if Windows is to be installed on it.