"Press Ctrl+Alt+Del to start" is a Windows function.
You appear to be trying to upgrade from a previous version of Windows, if not please give more details.
If you are upgrading from any XP or Vista 32 bit, you must do a clean instalation by booting the Win7 dvd. You can not do an inplace upgrade from XP or any 32 bit OS to Win 7 64 bit.
Remember to backup your files.