I have loads of programmes on my pc, but can anyone tell me which one are totally unnecessary??
Not without knowing what you have on there
Also programs on there own won't slow down the startup of the computer unless a part of them is being run at startup.
Click on the start button then run, type into the run box msconfig and hit enter, click on the startup tab and there is a llist of what programs are loading at startup, to dissable on take the tick out from next to it.
some things are obvious you don't need them running at startup, some are not so obvious, if you go to google and type the name in you can normally get lots of info on what each program does and if it's OK to disable it.