If you want to Anytime Upgrade then type Anytime in Start Search box to insert your Ultimate Product key, it will unlock the extra features in minutes.
If you want to clean reinstall, then boot the installer to overwrite Starter. I would make your Recovery disks first or save a Starter backup image so you have a path back if needed.
If Ultimate won't boot, where did you get the installer? Confirm ISO download or download another, burn to DVD using ImgBurn at 4x speed, or write to flash stick using Universal USB Installer
Use the Universal USB installer with Win7 in dropdown menu. Then boot it using one-time BIOS Boot Menu key given on first boot screen, listed under USB, Removable or HD's.
That's fine but you'll still need to activate Ultimate with it's own Product Key, since that machine is only licensed for Starter. How do you plan to do this?