All you have to do is very simple and intersting just follow the steps below:
1- If the file extensions are hidden on your system, first of all change ur settings to view file extensions. To do this, goto "My Computer" or any other folder and press this (Alt+T+O), with this you will see folder options.
Goto "View" tab and search for the "Hide extensions for known file types"
uncheck this option if it is checked. Now check your files, an extension will be shown at the end of all your files.

2- Now create a text document on the desktop. If you have enabled the extensions you will see ("New Text Document.txt") if you just see ("New Text Document"), you have to follow step 1. Then rename that text file to ("Flooder.vbs"). This will change the text file to a vbscript file.

3- Right click on the vbscript you created and click on "Edit". This will open notepad. Paste the below code in notepad and save the file by pressing (Ctrl+S).
Code:

'START OF FILE
'Flooder.vbs
dim wsh
floodlength=100 'lenght of flood
floodgap=50 'gap in each message in milli seconds
set wsh=wscript.createobject("wscript.shell")
wscript.sleep 5000 'wait before starting flood in milliseconds
for i=0 to floodlength
wsh.sendkeys i
wsh.sendkeys "{ENTER}"
wscript.sleep floodgap
next
'END OF FILE


Now login from http://www.mig33.com and enter any chatroom.
Run this script and within 5 minutes (5000 milliseconds - in the 7th line of code) click on the typing area of chatroom on mig33 website.

The code is very basic and simple to understand.
If you have any question about this, please ask me.
Good Luck!