The drive will have to be wiped, partitioned and formatted.
Read through the guides to installing Vista
Watch out for the part where it says 'Next you will select the location of the install. Select the drive, and then click on "Drive Options" to setup and Format the drive'
You can choose guide according to version you are installing (make sure it matches the product key you have) click here is the Vista Home Premium page for Repair, Uninstall, Upgrade, reinstall, install and Troubleshooting Microsoft's Windows Vista Home Premium Edition click here