md5sum and 3.1_r0a debian sarge

[John Que <qwejohn@gmail.com>]

Hello, 
 I am a newbie to Debian.
I had downloaded the dvd iso for debian:
http://cdimage.debian.org/debian-cd/3.1_r0a/i386/iso-dvd
This site is condisered the primary CD image server
according to http://www.debian.org.

(I downloaded it through http because there was some problem with my bittorent client; I know that 
bittorent/jigdo is recommnded)

Now there were 2 strange things:
It says there that its size is 4.7 GB.

However , the downloaded file was only 2.2 G.

Also when I went to other mirror sites  and click that file,
when getting to the "save as" dialog it was 2.2 G

Second, the md5 sum of that file did not correspond to  that of the file.

Can it be that the wrong file is on the site? 

And in case this is the problem - must I use Bittorent/jigdo  client ? 

Regards,
John