Office installation onto laptop - Error 1304

I have MS Office Professional Edition 2003 Home Use Program that I bought
initially for my home PC. I now have a laptop and am trying to load Office
onto that as well. The installation seems to start ok, although very slowly
between instruction screens. It then finally fails with the following
message;

'Error 1304: error writing to file: C:\Program Files\Microsoft
Office\OFFICE11\MSUSP.DLL. Verify that you have access to that directory.'

I am now stuck. Any help gratefully received.
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ACD