When is the last time you cleared all your cache files? That could be one problem to your IE, since I've found that no matter what the browser, once your cache gets large, it seems to slow the browsers down considerably. I use the following programs on a regular basis to keep my computer running smoothly.
cccleaner - first step. cleaner to clear all your cache files. This will mean you will lose some of your passwords like for AW.com, and will have to reenter them. Next Registry. See what is gunking that up and fix them. I usually dont back up my registry. Under Tools, startup. See what is starting up when your computer starts. A lot of it is crap and you can disable them. I recommend disabling them as opposed to deleting them. Since for some reason if you delete them, they come right back. Things like checking real player and itunes when your computer starts up is unneccessary, where checking your virus is necessary.
defraggler - after you run cccleaner, this is a defrag program. if you have never defragged your hd, then that could cause the slowing. My suggestion, before you leave for work, run defraggler. Once you start defraggler, on the top tab, there is an option to shut down computer after completion. Hopefully your computer will be done by the time you get back home.
ad-aware - it's a virus program like avast. I tend to like it a bit more, since they constantly update. And they have a gaming mode in case you are playing a game.
See if those help any.