Posted 12 February 2009 - 14:46
You should boot with the Win7 DVD. Press shift+F10, the command prompt will pop up. Enter "diskpart", then select your hard dirve by entering "select disk 0", then enter "clean" (WARNING: THIS WILL ERASE ALL DATA FROM YOUR LAPTOP, INCLUDING THE HIDDEN RECOVERY PARTITION CONTAINING THE VISTA INSTALLER - so you should first create a complete PC backup in Vista to an external hard drive, if you want to recover your previous settings later!). Then enter "create primary", then "active", then "format fs=ntfs quick" then "assign letter=c", then "exit", then close the command prompt window. Proceed with the Win7 installation as normal.
Alternatively you may create a complete PC backup, upgrade the Vista installation to Win7, test it, and if you don't like it, restore your Vista installation from the backup.
Note that you'll need a Vista DVD to restore your complete PC backup if you deleted the recovery partition. But you can use a Win7 install dvd as well to restore the backup images (if you don't have a Vista DVD), using diskpart to clean the drive, and then the wbadmin command-line tool, but you may also need to tweak the restored windows (use bcdedit tool if you run into the 0xC0000001 problem during booting the restored Vista) to make it boot properly.