While this key was a handy keyboard tool when there was no mouse, and when PCs were strictly for programming, this key is now so damn annoying! What do we need the “overwrite” mode for anyhow? How often do we use it to justify having the option?
It must be a fossil from pre-mouse days…
<a href=“http://www.straightdope.com/mailbag/mscrolllock.html”>Cecil’s take on the keyboard</a>
doh!
lol i am too durned used to typing html!
Well Shift-Insert is a way to Control-V (paste) with the right hand. But yeah I hate that key too.
Why? Without it, how would you toggle between “overwrite” and “insert” mode?
Fenris
I use it a lot. I could do without the Scroll Lock key.
Could be worse. You could have to use this baby.
Scroll Lock is often used now as a control key for KVM switches.
On the Insert key, I’ve just written a program that, although it doesn’t require it, caters for it. It is a lightweight text editor program to run in DOS (well, it is actually the front end for something else I’m working on) - the nature of the information that is likely to be entered into this program makes the ability to switch between overwrite and insert modes useful.
I accidentally bought a MS keyboard that has Insert assigned to Print Screen if F Lock is on. I guess this is so you don’t switch from Insert to Overwrite accidentally, because the F-keys have their numbers written on the sides and a variety of ‘useful’ functions assigned to the function keys when F Lock is off. This is overwhelmingly stupid. (For example, F4 and Alt-F4 both open a new window if F Lock is off.)
MS’s assumption that people are stupid and frequently press keys accidentally is made even more ridiculous in light of the fact that the keyboard has an oversize Delete key right next to Enter, and a slightly recessed button that turns the computer off in the top right corner of the keyboard. (It’s a Sleep key, which will crash many computers where APM is poorly supported.)
It also has only one context-menu key and one Windows key, which represents MS going back on its idea that people would use them.
If you do any extensive word processing, the advantage of having a key to toggle between insert text and overwrite text is very useful. This is particularly valuable when you need to use “boilerplate” and replace certain items – and while a global search and replace can work, often careful attention to specific language to be changed is needed.
As an example, I recently revised a will for a fairly well-to-do man, who had had the basic text, including creation of a trust, composed by a competent lawyer, but changes in his family and friends since he had written it made extensive modifications advisable.
I needed to revise and replace about a dozen specific bequests, adding some, changing the particular bequest on others, and deleting others. Being able to quickly overwrite the deletions with the additions, copying and pasting a single paragraph and then overwriting the modifications to make it a different bequest, and modifying the amount or objects bequeathed, made the revisions take less than an hour, where retyping the entire section and proofing the results would have taken over twice that long.
Likewise, drafting deeds for property transfer was a simple matter of changing identities of seller and purchaser, their legal addresses, and the metes-and-bounds descriptions of the properties in question. Overwrite saved me extensive time.
Yes, insert and overwrite are critical for writers. Jinx, if you ever write your novel instead of asking questions about it, you’ll see just how important it is! 
There is a program called ieScroll that uses the Scroll Lock key to allow you to toggle between IE windows only when you have a bunch of other programs open as well.
I use both scroll lock and insert. The latter to toggle between insert and overstrike and the former to do just what it says. I have programmed the text editor I use that when the scroll lock is pressed, the cursor stays in the middle of the screen and when it is not, the cursor eventually migrates to the bottom of the screen. Very useful when editing, as opposed to just writing. I certainly would not want a keyboard without both. On the other hand, if I didn’t want the insert key, I could program the editor to make some other change of state depending on whether it was on. That’s the advantage of using a fully prgrammable editor.
It’d be far better to crusade against the 4 or 5 instances of that one stupid windows key they put on keyboards nowadays to put a larger number of keys on the box in some sort of arms race, I think.
Hell, I’d love a fully-functional space cadet keyboard. But then, I’m a born-again Emacs fanatic. 
(Escape-Meta-Alt-Control-Shift forever, baby!)
To expand, Ctrl-Ins copies, Shift-Del cuts, and Shift-Ins pastes. Useful to me, because the brain-dead programmer responsible for the UI on a piece of Windows software I use at work remapped Ctrl-C to “Clear this form” and Ctrl-X to “Exit”. And of course, said programmer also failed to include the Edit menu, so no mouse access either. Without IBM’s CUA shortcuts above, I’d not be able to copy and paste.
What’s CUA? IBM’s Common User Access interface scheme – OS/2 and the first Windows used parts of it, including the above; later, MS added the familiar Ctrl-C, -X, and -V to Windows to help sell it to Mac users who were already used to them.