I agree with the person who wrote that the IE discusion was getting unwieldy, but I think I might have something to contribute in the general area, so I am starting this thread.
Firstly, anecdotally, I am 61, never expected to get a computer, but got persuaded about 18 months ago and imagine that if I can now manage to stay clear of problems - I didn't to begin with - then so can anyone, especially if forewarned, which I wasn't.
In any case I operate XPHome SP2, Internet Explorer (with Google and Yahoo toolbars) and ninemsn Premium, on a cooking-variety Packard Bell Celeron 256MB RAM.
And so to what I have found (if at the risk of some advertising):
I had trouble with Symantec (Norton) and so switched to McAfee, which I find far more user-friendly, supportive and hassle free ... though I found Privacy Service and SpamKiller to be unnecessary and a bit of a nuisance, at least with the safeguards built into Hotmail and the IE browser.
I tried a number of utilities to help keep my system clean and efficient and some of them were unnecessary/and or a nuisance, such as a defrag tool, when it is plenty good enough to use XP defrag frequently. Make sure you have automatic updates from Microsoft and McAfee, or other virus protection.)
It as well to be aware of some things on offer which are suspect, like Adware, especially when that looks like Ad-Aware/Ad-Watch ... which is excellent and well worth getting.
Spybot is another good utility and will actually root-out Adware, other so-called spyware stuff and heaps more, including Interet Washer, which should not be confused with System and Internet Washer, which I find very useful.
I also find Registry Healer useful.
That's about it for recommendations in this sort of area ... not saying that other good stuff isn't around, but these work for me (along with the pop-up stopper in Google) and when, a couple of months ago, I did have a hardware problem I couldn't fix, the profession commented on how clean my machine is.
As regards picking unwanted stuff up generally:
The thing is to never click on something you are not sure of and to never open a file which onboard precautions have warned to be suspect ... assuming you have a firewall, like McAfee, which responds to bad stuff coming in, or which Ad-Aware/AD-Watch lists for you.
At the end of the day, though, like when first learning to drive a car, you are naturally vulnerable; but then don't blame the machine/tools and try not to lose patience ... try to accept that as a "learner-driver" you will make mistakes and may have to pay in cash, or in an effort to sort things out.