http://www.tomshardware.com/reviews/...ance,3331.html
Looks like some HUGE gains going to Windows 8 and having to purchase GUI packages because MS tried to be Apple. *rolls eyes*
Easiest option instead of buying a windows 7 license would be to buy a Windows 8 Pro upgrade and then downgrade to Windows 7, while HP may not support it I highly doubt if you have sufficient searching skills and take advantage of things like... driverpacks.net you will have no issues getting the system fully functional with Windows 7, I'm still getting new Windows 8 laptops to run XP.
One more free option you could try if you are interested in just having a start button-
http://sourceforge.net/projects/clas...urce=directory