What version of DOS?
...
So, I tried to load a mouse driver in autoexec.bat and config.sys, by adding a line.
By mistake, I added a wrong line in config.sys and the computer stops while booting.
Tell us what the text of the line is. Exactly, if possible.
Since you seem to know which line it is, one way to work around it is to skip that line during boot.
I found reference to how to do it here:
http://www.computerhope.com/issues/ch000318.htm , it may be mentioned elsewhere on this site too.
Scroll down to:
"If you are running Windows 3.x or MS-DOS 6.x or below, boot the computer step-by-step to verify if a line in the autoexec.bat or config.sys is causing your issue. To do this, as the computer is booting...... "
and read that.
However, that didn't seem just right to me. Note that it has been a while since I've done it this way, so I'm fuzzy on it, and need to look it up.
So, I looked here too:
http://www.vfrazee.com/ms-dos/6.22/help/config.sys%20commands.htm ,
and scroll down to, "Bypassing CONFIG.SYS and AUTOEXEC.BAT commands".
Note that the vfrazee.com site mentions both F5 and F8, and the difference in their use.
[ The main page there is:
http://www.vfrazee.com/ms-dos/6.22/help/index.htm and is quite handy.]
I made a DOS Start-up disk but nothing...it doesn't boot at all!!! 
...
We need some more info from you.

When it "doesn't boot at all" , what does it do? What is happening?
Describe with detail.
How did you go about making the Dos boot disk?
What version of Dos is it supposed to be?
Any other info that you can think of, about anything mentioned so far, just might be useful. If you think of it, post it.
