a partial upgrade from 64-bit 11 to 12.04 doesn't complete. at "skipping windows environment (loader) on wubi system, done", it hangs up indefinitely. This is a dual-boot installation. Help !

You would be well advised to back up absolutely everything - both Ubuntu and Windows - and do a clean install before you get catastrophic failure. It is not a good idea to carry on running 'as is' with a wubi installation. Others might not agree, but my personal advice would be to remove the wubi installation using the Windows un-installer (usually safe but have your Windows install/rescue disk handy just in case). Then do a clean install of Ubuntu NOT using wubi - use the live-CD to install on a partition. This is fairly straightforward and should repair grub on the boot sector and save you future problems.

It depends on how far the upgrade has gone, and the reason for it hanging. There's little danger of losing the data on the Wubi virtual disk (just don't do hard reboots).

Since you asked this 10 hours ago, I assume you've rebooted and tried to see if it works. If not, please post an update stating where you are at.

Also please state whether you got low-space warnings on the upgrade, whether you had custom graphics drivers installed, ppa's etc. Also whether you have a backup of the root.disk.

Thanks

there was a proprietary driver for the video chip installed before the upgrade, which was 90% complete when the hangup occurred. It is not installed now. I do have the Windows repair discs for my machine, and I created a backup system image 6 days ago. I also sync my files between 2 machines, so the danger of data loss is lessened.

As of now, I can boot either to Windows or to Ubuntu 12, and I can navigate within either OS. However, Ubuntu's software update mgr does not work. Instead, I get a prompt to run a partial upgrade. This time, instead of trying the partial upgrade, which had failed so far, I opted to close the window. Then this popped up : 'Software index is broken. It's imposible to install/remove any software. Use package mgr "Synaptic" or run "sudo-apt-get install-f"in a terminal windowto fix this issue'

response to the 1st command : 'invalid operation install-f'

2nd and 3rd commands : 'E:dpkg was interrupted, you must manually run sudo dpkg --configure -a"

after 3 tries, 'configure -a' ran to its conclusion and got me back to the command prompt. Final report :

Errors were encountered while processing:
 memtest86+
 libpam-cap
 ubuntu-standard
 resolvconf
 libpam-gnome-keyring
 dictionaries-common
 samba-common
 smbclient
 ufw
 samba-common-bin
 aspell
 ubuntu-minimal
 nautilus-share
 hunspell-en-us
 printer-driver-pnm2ppa
 console-setup
 kbd
 pnm2ppa
 ubuntu-desktop
 checkbox-qt
 cups
 indicator-printers
 update-inetd
 printer-driver-hpcups
 bluez-cups
 printer-driver-gutenprint
 cups-bsd
 hplip-cups
 hplip
 sane-utils
 cups-driver-gutenprint
 checkbox-gtk
 grub-pc
 grub-gfxpayload-lists

Do I have to manually correct each error ?

install and -f are separate:
sudo apt-get install -f

$ sudo apt-get install --help
...apt-get is a simple command line interface for downloading and
installing packages. The most frequently used commands are update
and install.

Commands:
   install - Install new packages
  -f Attempt to correct a system with broken dependencies in place

I see. That is the big issue with command line prompts : no syntax errors allowed !

As of now, Ubuntu 12 is operating normally, thanks to your input. I was able to install and activate the proprietary driver for the video chip, detect and install my network printer, and perform software in a normal fashion. Error logs were even generated and sent to Ubuntu for analysis.

Thanks again for your input and your patience.

Thanks bcbc, that solved my question.