SUS will not install - service 'w3svc' (w3svc) failed to start

when installing MS software update service i recieve the
below message.

service 'w3svc' (w3svc) failed to start. Verify that you
have sufficient privileges to start system services.

i cannot get past this bit and have tried it on 3
differant machines. Is it a problem with sp4, as i cannot
see why i would have insufficient privilages as an
administrator