I am having problem playing a large Video file (48 GB) with avi extension?

I recorded a video using my laptop webcam. Then I backed-up the file in a Segate Free Agent Go Hard Drive (using encryption). Then I decrypted the file to my computer from the Free Agent Drive. When I try to play it, the Windows Media Player gives me an error message saying "the player might not support the file type or might not support the codec that was used to compress the file". I have tried to open the file by downloading Divx player, FLV Player, Essentials Codec Pack; all from CNet.com. But, I have been unable to play it. Was there any problem transferring the file from 'Seagate Free Agent Drive' or I don't have the necessary codecs. What should I do? I have Windows Vista.