the modification is not allowed because the selection is locked

I have office home and student 2007 (was preinstalled, and did activate it
when orinally bought machine)

For some reason I cannot use it as in word it says the modification is not
allowed because the selection is locked.

I could not uninstall the office home and student 2007 software using the
control panal in vista as i was getting an setup error message setup cannot
continue because a required file is either corrupted or not available . Run
setup again from original source disc or download location

so had to do it the long winded way as per instructions on microsoft's
website "How to uninstall the 2007 Office system if you cannot uninstall it
by using the Add or Remove Programs feature"

I then used microsoft's back up cd for my preinstalled software and it asked
me for my activation code etc and installed as i thought it would be okay.

I then went to use word and that's when i got the message at bottom of
screen saying the modification is not allowed because the selection is
locked.

Please help as the software is useless as a read only version!