First, you do mean ctrl-z (lowercase z, not uppercase, right?)

You could try this:
hit alt-f11 (to get to the VBE)
hit ctrl-g (to see the immediate window)
type this and hit enter.
application.OnKey "^z",""
then type this and hit enter:
application.OnKey "^z"

I'm hoping that the first one turns off the macro assignment and the second one
resets it back to normal.

If that doesn't work, then I'd start looking for a macro in a workbook that
opens when excel opens that steals this assignment.

Chip Pearson has some notes on how to diagnose startup errors:
http://www.cpearson.com/excel/StartupErrors.htm

And Jan Karel Pieterse has more notes:
http://www.jkp-ads.com/Articles/StartupProblems.asp

wrote:

hi there

some muppet has reassigned Crtl+Z to a macro and i cannot find where to
put it back to 'undo'

any ideas?

I have been through the 'help' and know how to do it if i knew where it
was,

--

Dave Peterson