Vista SP1 unlike WIndowsXP is a very paranoid update. It fears to be
installed on problematic machines - with hardware known to cause problems.
If your hardware is blacklisted by Microsoft, SP1 will NOT show on WU
updates list and you won't bve able to get it automatically.

If you force standa-lone download & installation, you risk running into
problems.
Two workarounds:

1) Find if problem hardware manufacturer offers updated drivers, then re-run
Windows Update again, see if it now likes your hardware
2) Do NOT bother and wait until Windows7

Vista was a step backwards for Microsoft, the entir epurpose of WIndows7 is
to undo Vista's harm and get back to hwere MS was with WIndowsXP, a;beit at
a new more complex/more powerful level.
Just wait for Windows7, don't wazste your energy on Vista anymore, it's a
piece of you know what....