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try restart and hold the shift key pressed. that might give you an option of choice (Depending how old you mac is.
by PeWi on Mon Sep 6th, 2010 at 02:54:52 PM EST
[ Parent ]
ah sorry that is safe more:

Restart your Mac while holding the Option key on your keyboard until boot options are displayed.

by PeWi on Mon Sep 6th, 2010 at 02:57:00 PM EST
[ Parent ]
Interestingly on this site:
http://support.apple.com/kb/HT1343
the command option is not listed, but you can try

press holding X during startup, as it apparently
"Force Mac OS X startup (if non-Mac OS X startup volumes are present)"

by PeWi on Mon Sep 6th, 2010 at 06:09:54 PM EST
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