It is my understanding you
cannot upgrade from Vista Home Premium to W7 Professional without a clean (custom) install. The regular upgrade option is only available from the same version to the same version or to Ultimate. See
HERE that custom installs are needed to change from Home Premium to Professional.
To do the clean install you want to download
Windows Easy Transfer for Vista and use it to back up your user settings and data. You should also gather all your program disks as you will have to reinstall all your programs after the install.
Note that HP likely installed some software for you and you will need to download that from HP or find a replacement or do without. Most of what they loaded you probably never used or it expired after a x-mos test period but they usually have a few things you may want such as software to use the touchpad if the standard W7 drivers don't work, or to use extra keys on the keyboard, or an on screen volume indicator.
IMPORTANT: HP recalled a lot of the batteries in that notebook because of overheating. You might want to check out
HERE to make sure your battery is safe. That is also where you should find most of the programs to download that HP installed for you but are NOT part of the OS.