|This is the way I understand the recovery disk/partition.|
You have a recovery partition, so that if your install of the c drive goes bad, you can restore from the D partition.
But if the complete drive, c & d goes tits up, you have the recovery dvd's to restore that, or a new hard disk.
Obviously, these are only to the date you got the pc. Ghost is a good way of making regular backups with you latest programs & documents.
I used Ghost 2003, until I discovered Acronis Trueimage. Ghost 2003, is not easy to back up to usb drive. You could backup the complete disk to dvd's, but that could mean a lot. With acronis, you can back up to usb. Of course. it is not free, but Seagate have a disk clone utility, which is a cut down version of Acronis.
Until recently, I had created a separate partition, then I used ghost 2003, to create an image of C. This isn't foolproof, but it was a quick way to restore, when I had a problem.
Before posting try google. Backup. Use anti virus software.