Varadar,
If you use your Vista HP Recovery Discs to return the computer to a factory like state, then run ABR "backup.exe"... you will have a valid Vista Home Premium OEM SLP key and certificate that is only good for installing a "clean" copy Vista Home Premium on that computer. It will not work with any copy of Windows 7, as Windows 7 and Vista use a different "hash" to validate the Windows product key. You would need a valid Microsoft COA with an unused Windows 7 key to install Windows 7, if the computer didn't already come with Windows 7.
Using the HP Recovery Manager or a HP Recovery Disc set isn't the same thing as installing Windows from a Windows installation disc. if you already have created a set of recovery discs and know that they work, you can delete the recovery partiton during the installation of Windows. If you every need to return the computer to a factory like state, including the recovery partiton, just use the HP Recovery Disc set.
Please send KUDOs