Why is it that I’ll be typing something, and when I go back to edit it or try to type something earlier in the text, the new letters I’m typing will start erasing the letters in front of it? It really pisses me off and wastes alot of time. Why does this happen, and what am I supposed to do to fix it if it happens? (This isn’t only here, it’s on IM’s, Word, etc.)
In MS Word, you can press the “Ins” key. On the status bar on the bottom, the “OVR” (overwrite) should go off.
This happens when you accidentally hit the Insert key to the right of the <–Backskpace key and above the Delete key on most keyboards. This also happens when I accidentally hit that key. It’s obviously a conspiracy, since I can’t think of a single practical use for that key, and I can’t think of a single non-malicious reason for placing it right there.
To expand upon seth’s point: When typing, you can be in ‘insert’ mode, or ‘overstrike’ mode. If in ‘insert’ mode, you are inserting text where the cursor is, and the existing text is moved out of the way - this sounds like what you want.
When in ‘overstrike’ mode, each character you type replaces the character to the right of the cursor, if any.
To switch between modes, hit the ‘Ins’ or ‘Insert’ key once. You may need to experiment - put your cursor in the middle of a word, type a letter to see if you are in ‘insert’ or ‘overstrike’ mode, hit ‘Ins’ once, type another letter, verify your mode has changed, etc.
Enjoy…
Ah yes, the Insert key and his brother Scroll Lock.
Remember these next time you want to drive a co-worker completely nuts.
My record so far is 55 minutes before the unsuspecting victim figured it out.
Only works once though.
O.K., I’ve had the insert problem, easily fixed when you know what to look for.
Sometimes, however, when I’m working on a manuscript and I edit alot, when I resume typing the letters will slightly overlay each other.
'splain that.
This often happens if you have software that defaults key states for you. A lot of computers can preset things like Numlock, Scroll lock (What is it even?) and caps lock(Why?).
When you first turn on the machine, look for a message saying “press Del [or esc or some other key] to run Setup”
You’ll be surprized at all the useless buy non-overridable settings there, like repeat-key rate.
Functions:
[ul]
[li]Scroll Lock: Back in the Late Plestociene, computers used text-based interfaces. That means you actually had to be able to read what it gave you. Kind of hard when you want to view a disk’s directory and the text is going by so fast it’s blurring. So the Scroll Lock key locks the scrolling text in place, enabling you to read it.[/li][li]Caps Lock: Certain systems only accepted capital letters. To make a capital letter, you either press and hold Shift, a time-consuming task that becomes tiresome if you have to constantly let up on it to type numbers and punctuation marks/symbols, or you just punch the Caps Lock button and type as you always have.[/li][li]Numlock: On a standard numeric keypad, numbers share keys with cursor-control commands (the arrow keys, mainly). If you want numbers and numbers only, punch that and type away.[/li][li]Insert: Well, some people just expect an overstrike function. It must date back to typewriters (you know, word processors without screens) when an insert function would have been physically impossible.[/li][/ul]
Almost all of those keys are now anachronistic. They still exist because they still have ASCII designations and, dammit, they’ve always been there! Hey, we still suffer through QWERTY, an even more anachronistic system.
Ohh ok then… thank you! 
At one place I worked, when I would scroll down through a document I was editing, the cursor would delete letters or overwrite them with a different letter.
The computer guys diagnosed this as a bios problem, and now I believe that computer found a new career as a boat anchor.
So that can be a possibility.