You could try the stand-alone SP1 update. Many have success with it when the "normal" update fails. You will need SP1 installed to install SP2. SP1 will not give you any great speed increase. If your machine has slowed, perhaps you need to clean it up by removing un=necessary programs, cleaning the Registry and removing junk on the hard drive.
Windows Vista pc works fine, but for some reason A bug prevents me to add kb936330 sp1 use win updater faster then the full download, I  known wait some time more reliable version sp-1 be a while for Sp-2 patch I not known release just a guess imply originally . I only add new patches turely fix windows I like how pc works now  .Will   kb936330 patch get back performance I lost Pc used to have . A year back could the sp1 patch speed up things for  i 530 tower pc upgraded 4gb still not get what able get performance  Inet plug ins work like they did PC was new , prefer easy fix then reformat PC unless for serious reason as my lose printer again? Thanks for all the help detail what I needed . .:emotion-42:
Vista sp1 many fail install attempts kb936330 sp1 Help any performance boost 
prefer A easy fix