Delphi 5 patch doesn't work ?!

We are using the delphi5 enterprise, (it's not the trial version), I
downloaded the patch from borland and tried to apply the patch, it asked me
for the serial # and license key, I keyed in the one we used for the
installation, but it always told me the combination is wrong, is there any
other stuff we missed?
how can we do?

please help !!