You can attempt to run Recovery by tapping the key given on the first boot screen, or read how in your Manual on the Support Downloads webpage for your computer model. You may wish to run Recovery so you can make Recovery Disks from it which put you back to factory condition while also allowing you to wipe the HD to get the cleanest possible install.
Or you can save externally a Windows 7 backup image of your factory install so you have another method to reimage the HD to get back to HP.
Then your options are:
1) wipe the HD to give Windows 7 the cleanest possible slate for a clean install of Ultimate. SSD / HDD : Optimize for Windows Reinstallation
2) Use Anytime Upgrade which unlocks the greater version by inserting Key. You can use your Ultimate key for this, according to many reports here.
3) We can show you a workaround to in-place Upgrade HP to Ultimate.