Hi
Welcome to Microsoft Answers!
We cannot install vista using a recovery disk. A recovery disk is a general term for media containing a backup of the original factory condition or favored condition of a computer as configured by an original equipment manufacturer (OEM) or an end-user. You can restore your computer to factory settings using a recovery DVD.
When you do a complete pc backup choose C drive so that it does not install on the D drive.
OR
You will have to use a retail vista disk to format and clean install vista on the C partition.
Complete pc backup
http://windows.microsoft.com/en-US/windows-vista/Back-up-your-programs-system-settings-and-files
Installing windows
http://windows.microsoft.com/en-US/windows-vista/Installing-and-reinstalling-Windows
Hope this helps.
Thanks and Regards,
Bindu S Microsoft Support
Visit our Microsoft Answers Feedback Forum and let us know what you think