Alan
I am not sure how upgrades are fundamentally different from clean installations but I suspect that you need a bigger external drive to backup to so Windows 7 can create a VSS or Shadow Copy. You may be able to borrow a friend's external drive for a night
or else spend $100 or so and get at least 320GB HDD.
I find it helps to do a minimal installation then make a backup then try to reinstall Windows 7 from the backup. Good luck as it takes three to six hours usually including checking various Accessory programs to see that all work.
The problem I encountered is that Windows 7 Backup was working fine for about three months then appears to hae stopped working on all eight of the ten computers my family use for work, study and entertainment. I already own a copy of Acronis and that is
said to work although the one and only time I tried a restore with Acronis it did not retain security codes and login IDs.
Your other choice is to go some version of Linux (one form of which is Apple)- Windows is such a dog that I often think it may be worth the change if you intend to use any machines for mission-critical or other production work.
Cheers
I M Gadget