Vista - Access Denied for automatic updates

When I try to update from website, it tells me to go into Services and BITS
to change settings. I get "access denied" when I try to enable automatic
updates from services. The startup type is disabled. Service status is
stopped. the path to executable is
"%fystemroot%\system32\svchost.exe-knetsvcs". When I try to start BITS,
error 2 comes up "The system could not start BITS on the local computer"
"The system could not find the file specified". Path to executable for BITS
is same as above. I've already run Windows Defender, Malicious software
removal tool and have McAfee virus remover but can't seem to get this error
to go away. I'm not computer savvy so tried to follow other messages on
topic and got lost when they talked about going into the registry. Please
help! I have Windows Service pack 2, my computer is Windows XP.