Calc file won't open

[goodengansey]

I have a calc file (1,16 Mb) which refuses to open.
I get the seagulls on a blue background icon, which stays onscreen for as long as I care to leave it (2 hours +).
Task manager does not find it so the only way to escape is to reboot Windows.

I have searched the forum for a solution and done the following:

Reset the "user" as described here:
viewtopic.php?f=74&t=12426

I have (repeatedly) deleted the lock file associated with the document as described here:
viewtopic.php?f=9&t=90832&p=429686&hili ... en#p429686

I have renamed the files extensions.pmap and extensions.db as described here:
viewtopic.php?f=74&t=12426

I have uninstalled openoffice and re-installed Apache_OpenOffice_4.1.5_Win_x86_install_en-GB

I have also reinstalled Windows (7).

I have many other calc files, all of which seem to open OK - so it seems to me that the problem lies with this one specific file.

Can someone suggest a solution please?

[RoryOF]

OpenOffice files in ODF (i.e., OO's native formats) are zipped archives. Outside of OO make a copy of the file and rename the copy to type .zip. Double click it and the system archiver should attempt to open it. If it fails, please note the error message and report back. Preserve the original file unmodified; we will need to have that for any recovery attempt, although don't be too optimistic.

[goodengansey]

OK - have renamed the file .zip
When I double click it opens as a directory containing the following:
configuration2 (directory)
META-INF (directory)
Thumbnails (directory)
and
content.xml
manifest.rdf
meta.xml
mimetype
settings.xml
styles.xml

[RoryOF]

So far, so good. Now see if you can open content.xml with a plain text editor such as notepad. This should open as text, albeit with XML tags. If it doesn't open, or is non-text garbage, the file is damaged.

[goodengansey]

Yes - I've got a million miles of text

[RoryOF]

Then there is hope that the unaltered original file can be opened. Often this can be done using a version of OO on a different operating system. Before doing anything else, I'd suggest shutting down your computer, rebooting, and immediately trying another copy of the original file in OpenOffice; t might just work.

[goodengansey]

I've alredy tried several times to open another copy after rebooting - all with no success.
It won't open on a different system either.