Download the MD5SUMS too. All it is is a text file with a list of MD5 hashes.
Then what you need to do is get a MD5 sum generator. What this will do is create an M5D hash that you can compare with the one in the MD5SUM list you have downloaded.
If they are different it means that the .iso file you have downloaded is corrupt and may not work correctly.
To check the MD5 sum in linux do:
Code:
md5sum <path to the file>
However if you have downloaded and are burning the disks in windows you will have to get a MD5 sum generator for windows
(However, all of what i have explained may not fix you problem, it is just to check that the file downloaded correctly)