Lizzie, get them to stick with IE, it's more secure than the alternatives.
But after any suspected compromise on a desktop, don't use software to clean, rebuild 
Cite your source my friend. With the exception of Chrome, IE is the worst of the mainstream browsers.
FF with some handy Add-On's is perfectly safe, perfectly stable and far quicker than any other browser out there.
I disagree, IE is the most secure of all Windows based browsers, with the added bonus of updates being built into Windows, so soon becomes blatantly obvious if the update mech has been compromised.
My source? The myriad of security notifications I have to sign up to in a professional capacity. These range from the standard government CERT organisations around the Western globe and vendor notifications, to the commercial based threat warning organisations.
NOT from lazy, useless IT journalists writing in popular IT journals, who simply do not know their arse from their elbows (and spout crap like "Vista is shit" when it came out, as they were too lazy to work out how to use it).
Not much comes out from IE. That and its inbuilt, secure update mechanism would make me recommend it for most Windows users.
A reasonable amount comes out for FF. I use this as my secondary browser, but would only recommend to IT savvy people (which rules out most who think they are
*)
Tonnes comes out for Chrome, as its inherently broken (on all platforms)
Safari under Windows leads to interesting vulnerabilities that are not the fault of either software per se, but what is called a blended threat. Best avoided on Windows.
Opera uses a different model altogether, not really relevant for Windows PCs.
HTH
* Most people who use known/common fault or primarily (in this day and age) Google as primary sources for fault finding.
I have a knack for spotting them - probably all those interviews I've had to do every time we've needed staff. I've been on a Redhat 7 rapid track course all week (Redhat 7 is very different from earlier versions - init process replaced with system, firewalld replacing iptables ifconfig's deprecation in favour of ip and nmcli etc etc), and at the end of day 1, on the way home, I said to a colleague who was on the same course, 2 people I said were out of their depth here - both were the "I've had 30yrs experience, and I know all this stuff, no idea why I've been sent, yada yada yada.
During yesterday's exam, one left after an hour with some excuse about not being able to do it, other was getting examiner over constantly with complaints about mouse and keyboard not working, all of which were user error.
That said, my results haven't come through yet, so suppose it'll be Monday now. Squeaky bum time
