[invisible]

This is like saying that saving taxpayers money today is saving the taxpayers money in general. This is totally untrue - 5 years of malware, support tickets, etc. that need not be there costs way more than doing the transition now versus having to do it later anyway.

[MichaelApproved]

Aren't anti-malware software and similar expenses needed regardless of browser version? This is a cost that can't be avoided so the upgrade isn't going to eliminate that and save money in the long run.

[invisible]

It is my experience that the risks are exponentially higher the further you get from the "flagship" product. This is also true for Firefox - if you don't update as updates become available you will soon find yourself with something bad on your machine if you're not careful (and on Windows). Plus, while Windows 7 built-in protection isn't great (which, if they went past IE6 they should upgrade the OS too), it does prevent some massive system-wide changes and rootkits.