Ok so I bought a new keyboard, the microsoft natural ergonomic 4000 v1.0.
Ive been using it & running into a problem that I cant seem to figure out. I googled several phrases but came up empty on them.

When Im typing either in private messages, or word pad, etc. I seem to be hitting a key that is activating a function that does this. When you type text and make an error jump back the cursor to the error then retype your letters and notice your previous letters are erasing and getting written over. The more you type the more the previous text disappears right to the end of the message or paragraph thus retyping & trying to remember what you wrote.I found a little trick to get around this problem but I would like to know what function Im hitting so I dont have to dance around this.
What is this function that Im activating on the keyboard? Does this happen to anyone else?
Its driving me nuts.