Peter..
This very small & free app might help.
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http://free-backup.info/justzipit.html
That's all it does & very quickly.
Instructions on site.
Of course, there are heaps of others.
7Zip is also very good.
ps. This oldie might come in handy?
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http://www.midnightkite.com/dansoftware.html
Ooo.. Gives you a chance to use JustZipIt in reverse.