Cant extract .rar file. help !!!

[on the high]

have downloaded 3 .rar files for installation of a software, 2 files of 600+ MB and one of 400 mb.
while extracting with winrar i ge the following error, " the archive is ether in unknown format or damaged" have tried downloading the 400 mb file again, this time continuously without pauses or breaks, but still no luck. renamed file to zip, tried repair by winrar and advanced zip repair and yet no luck.

anything else i cant try. need to get this to work. very important software.
anyone any ideas?

 

[Nodsu]

Very importand sotware on three piated CD images?

Please tell us the exact names of those files and the exact procedure how you are trying to decompress them.