We want to prevent downloaded files from corrupting. So use Hashtab to check that. 
1. Download Hashtab2 from the following link: 
Code:
http://www.4shared.com/file/105239290/34806082/hashtab2_setup.html

2. Then install the file. 
3. After installation right click on the extracted iso. 
4. Click on the "File Hashes" tab and wait for the hash to load 
5. Now check with the following: 
http://img685.imageshack.us/img685/1512/hashw.jpg