Vista uppgrade to legal Win 7, but a friend installed a pirate versjon

My friend got some help from another friend of her to uppgrade from Vista to Windows 7. Instead of installing the uppgrade versjon she had bought, he installed a full version 7 pirate copy. And of course, it is not possible to validate it.
So, I wonder, can I do a clean install with the uppgrade version of Windows 7, without installing Vista first (again)?
And, is there any change that the hidden recovery partion with Vista unfortunately can be deleted?

I would Clean the HD Drive first, using Step one in this tutorial:
SSD / HDD : Optimize for Windows Reinstallation

Everything you need to remember to back up, as well as the actual install steps with tips to get and keep a perfect install is provided in Clean Reinstall - Factory OEM Windows 7 and are the same for retail Win7.

When you boot the installer for your licensed version it will see an OS on the HD and allow use of the Upgrade key during install. If not Skip it and afterwards do Option 3 in Clean Install with a Upgrade Windows 7 Version to activate Upgrade version on a new or cleaned HD.

If you're prompted during activation for how many PC's this key is installed upon, it may mean someone has used your key on another PC. The only answer you can give is one, which will deactivate that key on any other PC when it connects to the internet. MS Customer Service can help you if necessary.

Everything is explained in the Clean Reinstall tutorial but to recap be sure to delete all partitions during booted install, then click Next to have the installer create and format your install partition or do it yourself if you have a particular scheme in mind, at Steps 7 and 8 of Clean Install Windows 7 .

Have your network adapter in the backup so if it isn't provided you can install it to get online and do all rounds of Important and Optional Windows Updates, after enabling Automatically deliver drivers via Windows Update (Step 3) . After requested reboots go back to Check for Updates until they are all done.

Then if any drivers are still missing in Device Manager, import them from the Support Downloads webpage for your PC or device.