Windows Vista A whole lot of Update problems

Hey,
I have had issues with my computer (Acer TravleMate 5530G) and a lot of programs for example iTunes wont install and i get a load of different errors. I have a fair amount of experience of computer since i like to play video games and just surf for fun (not a nerd though). I have never learned to fix intimidate computer errors since i don't want to mess the computer up... I have visited several forums and i have noticed that most of my issues are common problems and i have traced down the syndicate, Windows Updater. I have learned that this is causing my issues because the updates are off course important to the computer. Here lie the problem:
1. My computer was good for about 5 months until i went risky and started downloading unsecured stuff from the web. My Updater "crashed" and i don't know the reason. Firstly it does not check for updates, error 80080005. This went on ever until last week when i experienced something else with leads me to 2.
2. My computer suddenly got the shield on the shutdown button in the start menu witch means i have updates to install (right?). I shut down and it installed 30-40 updates and the most of them succeeded some failed. (I came to learn later that only microsoft office updates work the vital important updates like vista all fail) This happens now every time and all of the updates fail. Why?
3.I do not choose to download or install or even check for updates because i get several errors.
I chose to ask you because i read some threads and most of the people whom need help really got it from you unlike all the other forums where the solutions just spawn a new problem.
Thank you so much in advance
Sebastian