(If I'm not wrong... You can put this at the start of each sentence
)
The upgrade advisor advises for
windows upgrades cd/dvd.
It advises you to get the windows 7
home premium upgrade, because you have windows vista
home premium.
Those upgrades
allowed to install windows 7
over windows vista (and maybe also over WinXP),
without to allow a clean install.
They cost less than a
FULL RETAIL dvd, because
with this last one we were able to do a clean install.
Unfortunately, windows 7 upgrades (for windows vista) are no more available, it seems.
And windows 7 full retail dvd are becoming rare.
IIRC, we (my family) did a similar procedure when we had windows 95: we upgraded it with windows 98, but it didn't allow to do a clean install.
Hence the problem in that case was if we had to reinstall windows: first we had to reinstall windows 95, then we had to install Win95 updates, then we had to upgrade it with windows 98 upgrade cd, then we had to install Win98 updates.
You can substitute win95 and win98 with win98 and winME, or with win2000 and winXP, and so forth (not sure if those upgrades were available; this is just theory).