I recently had a major hard drive problem...just after downloading MS updates ! I had an error showing as " bad patch" and it was impossible to open up windows, any files or even get system restore to work. It could have been a virus, but I do have " protection"...but subsequently I did a full hard drive factory restore . The speed the puter works at now is much better. As such I would tend to agree that we stick too many superfluous programmes in, and hardly take anything out.
One big issue is I tunes...feck that thing is self colonising ! I dont have it on my hard drive now...but previously I could not remove it from the start up menu ...the thing was always working in the background ( spying on me I reckon ! ) ....feck it off if u have it.
Also - do you have windows defender / firewall running as well as AVG ? That will slow it all down too. I also heard AVG went bust ...so all yer virus definitions will get out of date rapidly and you will be open to attack.
Also , yer actual useable ram may be a lot less than you think, and some programmes need vast amounts of ram to work...which slows it all down yet again. My missus laptop supposedly has 3 GB ram, but it has precious little left after the operating system starts working ! I also think windows vista uses far too much ram just to operate...I used to be able to switch off a lot of the effects etc, but updates seem to have taken this facility away.
IMO its a bit like adjusting suspension! - take it all out( programmes) ...then monitor progress and effectiveness as you put it back in !