wubi grub boot problem

Usually this is due to NTFS corruption, possibly from hard shutdowns of Ubuntu.
See if this helps: http://ubuntu-with-wubi.blogspot.com/2011/08/missing-rootdisk.html

Also check this out for the future: http://en.wikipedia.org/wiki/Magic_SysRq_key#.E2.80.9CREISUB.E2.80.9D_.E2.80.93_safe_reboot

Thank you for your reply. I have started 'chkdsk /r' on the partition where the Ubuntu 'root.disk' is installed - 'Local Disk4' of four partitions (Local Disk1-4, but it is taking a very long time!). All files, including 'wubildr + wubildr.mbr' seem to be installed OK.

What puzzles me is this: Thinking there might have been a corruption of the ext4 files, I deleted Ubuntu using Wubi delete and re-installed. I checked that the 'boot.ini' on 'C' was modified back to 'just XP' and that the Ubuntu directory (on Local Disk4) and its '.disk' files were gone.

The install went OK - until the end when it went into reboot and I then got the GRUB> prompt back !!? i.e. no forced power-off/reset occurred?!

Are you suggesting that any previous forced power-off/resets will have corrupted the NTFS formatted disk? Surely this would show up when Wubi was doing the install? I have had no problems inspecting this partition and the others in XP. (?)

I would appreciate your thoughts on this. Many thanks.

Uninstalling Wubi will have deleted the Ubuntu install (and everything contained within it). Hopefully you had important data backed up.

I think there are many variables at play with ntfs corruption as to 1) what is corrupted and 2) how corrupted it is. In some cases, windows will detect it automatically and move corrupted files to a FOUND.000 folder. In other cases it will only do this when you run chkdsk. In some cases, chkdsk will just fix the problem. Sometimes the whole \ubuntu\disks directory is corrupted.
Why uninstalling worked for you, but reinstalling still wouldn't boot? Dunno (sorry).

Without trying to speculate on what the exact situation is, the steps that resolve it for most are:
1. chkdsk /f (fix any existing ntfs corruption)
2. make sure the important files are still there and check/clean up files within the FOUND.??? directories

Just to let you know what's happened.

I scanned the partition where Ubuntu was installed (Local Disk4) and the C drive/partition (Local Disk1) with chkdsk /r (I believe /r implies and includes /f). No errors were found in either case and no 'found folders or files' were created or are present.

Tried Ubuntu - still hanging on grub>. Uninstalled and reinstalled using Wubi to the same partition - still the same !?

This time thought I'd install to a different partition (Local Disk3) - success - Ubuntu boots! Now getting back to where I was with it in terms of apt updates etc. - but in a minimalistic manner until I know it won't fall over again soon. Don't understand how it now boots OK just being installed to another partition?! Have noted the mnemonics to interrupt and regain control on any future lock-ups, etc. :-) :-)

Thanks for your help.

Thanks for the feedback. That is rather strange... that it booted fine before, but suddenly refused to.

Maybe you can run the bootinfoscript sometime and pastebin the result - see if something interesting shows up. http://bootinfoscript.sourceforge.net/