Where can i store a string ???

English aint my first language.
Hello,
Im working on my chat server/client again, and i want to create some kind of "history"
I mean, To save the old conversation.

So i thought i could save the textbox as a string and store it in regedit
using simple method But it seems like regedit got some kind of Character limit, and makes my client crash.
Where could i store that string ?

I thought about a .txt, but .... I would prefer if it could be "stored" somewhere, avoiding possiblity of deleting .txt files
i want the history to show in my Project, and not in a Notepad, thats also the second reason

Any1 idea ? Thanks !