That suggests you're using an out-dated installer. See:
http://support.microsoft.com/kb/300451
Alternatively, you may be installing from a user account instead of from an administrator account. See:
http://support.microsoft.com/kb/838687
See also:
http://support.microsoft.com/kb/928218 and
http://support.microsoft.com/mats/Pr..._and_Uninstall
The simplest and quickest fix may be to use Windows' System Restore to restore your system to the state it was in before you uninstalled Office. FWIW, there is very little than uninstalling/reinstalling Office will fix that an Office repair won't.
Once you've done that - and you've repaired Word (eg via Word Options|Resources|Diagnose) - post a new thread in the Word forum about whatever issues you are still having with Word.