So, I bit the bullet and decided to retire Vista Ultimate and install Win7 Home Premium.
First attempt: from Vista desktop I put the Win7 DVD in the drive and selected the install option. Started well, rebooted partway through the 'expanding files' section, picked up again from where it left off, but then froze; frozen mouse and no disk activity. Rebooted.
Second Attempt: decided to just wipe the hard disk (had already backed up Users directory). Started well, rebooted partway through the 'expanding files' section, picked up from where it left off, but then froze again (at an earlier point, only 17% done instead of previous 39% done).
Third attempt (getting worried now because I had blown the previous Vista install away entirely now): decided that something was switching off a some hardware or something, decided to keep mouse moving while installation executed (also had vague idea that OnIdle processing was being used so moving the mouse might help). No freeze! Hooray. installed.
First boot: All set up with admin user. First things first, install USB Wifi from the Vista drivers I had thankfully remembered to backup to thumbdrive. Halfway through driver install and it froze! Oh no, here we go.
Second boot: got further this time, managed to install USB WiFi and get to internet before freeze.
Third boot: kept mouse moving at all times. Got to internet, googled Win7 Freeze, got pointer to change power settings to 'high performance' to keep everything on all the time.
Two hours later: no freezes yet, but time to go to work. All drivers installed and a Windows Updaet ran (interestingly Windows7 has updates already, nice to know they haven't gone on holiday!).
So tip: if you get freezes during install, keep the mouse moving. If you get freezes after install, change power settings.
First impressions: not staggeringly different from Vista, but so far so good. Media Centre works with slightly different UI, found my tuner and found all the Channels I had before.
Will no doubt spend this evening restoring all user files and installing applications, so we'll see what differences there are when there's more to do than play Solitaire.
How did everyone else get on?
Herbie