by alright you should be able to use the windows 8 to upgrade from win 7. BUT it does not always work!
you should use a program to back a system backup of your current windows install and backup any personal data (music, pic's, Doc's, Etc) before doing any upgrade.. i recommend backing up to a second hard or external hard drive. so if the worse happens you can always restore it back.
i personally have an external hard drive which i backup too. i use 2 different programs to do 2 different types off backup.
EaseUS ToDo Backup Free i use this to do a system backup of my current windows installation and also back a bootable recovery dvd or usb pen drive.
FileSyncFree i also use to copy all my data (again pic, music, doc's, etc) to my external hard drive.
Okay one final question. I ran Windows 8 Upgrade Assistant and it said "Secure boot isn't compatible with your PC. Your PC's firmware doesn't support secure boot so you won't be able to use it in Windows 8."
What's secure boot? Does it even matter if it's used or not?