They can be prevented from loading, but most of them will then reinstate themselves the next time you run them.
I tried to disable a number of non essential apps using msconfig, but found, as you have, that they just re-instate themselves next time the P.C. is started. I spotted a tip on a help forum which gets round this: tick the "selective start up" box. The next time you reboot a window will advise you of this, but click on the "don't remind me in future" box and you won't be troubled with every app on your P.C. trying to run on start up.
Hope this helps.