It seems you have quite a few options:
1. Use another backup program (you didn't tell which one you use now)
2. Configure it the way you like in stead of the way it is configured now.
3. If it's a full backup: manually delete the old backup before you write the new one 4. 4. If it's an incremental backup: delete old files from it (the files that you deleted from the c: and don't want back); they could take a lot of space over the years.
5. Backup to another device.
Most laptops I know of, have only one hard disk, that is partitioned into 2 drives, the c: and the d: drive. In that case a backup like you describe could be useful when you have to reload the OS, but only assuming 3 critical things: (a) the reload of the OS doesn't touch the d-drive, (b) you know how to restore from the d-drive, (c) it's not an encrypted backup with the encryption key overwritten by the OS reload. And such a backup doesn't protect in the least against a physical failure of the hard drive, because that same drive contains both the original and the backup copy and both are lost.
My laptop is configured to run weekly back ups to my D Drive. However it appears to want to create an additional back up to the one that already exists, rather than overwriting the existing. This causes it to return a report that the last back up failed (as there is not enough free space on the D drive for the new back up). How can I make sure that the back up overwrites the previous one?
I'm running Windows Vista on a Dell Inspiron 1525.