During typing anything using keyboard in a word editing program or in a compiler program.
I have often come across this problem and it becomes so teasing to me. But Now I have found a solution to this problem. Whenever I have typed some words or sentences and I do want to change that word or sentence it does change but will overwrite on other words so previous words will be deleted. This problem is due to mistakingly pressing of Insert Key.
When we press Insert Key it does set the function mode of the keyboard to Overwrite words.
Solution
You do need to Press Insert Key again to set the keyboard function mode to Insert words rather than Overwrite words.
The figure below provides the layout of Keyboard showing Insert Key

Sufi007
Nice info
I am having problem in MS Excel, when I click on a cell it changes into edit mode rather than highlighting/selecting it. Any solution for that?
MS
Information is here, but presentation suffers. But best way to improve this entry is to state the problem & the resolution in a much briefer and simpler way and improve sentence structure. (Have someone who writes English well review and/or do the actual edititing. Nice to add visual to show where insert key is for those least familiar with the keyboard.
Sanix
@MS: Thanks a lot for the suggestions. Although the author of this article is not available, I have noted down your suggestions and will take them into consideration on new troubleshooting articles.