Problem Installing

The MD5 or SHA1 value generated for the file does not match the value you entered as the check sum!
Either the file did not download properly, or the MD5/SHA1 value entered was not correct.

What dose it mean, and what can i do to fix this, my problem is that i canot see the patch 's to update when you launch PWI, i get every options but it makes me update because i just downloaded the game. I have downloaded all the manual patch's. I'v been trying to play PWI for the past two days, the massage above popup's when i try to re-install PWI it ask me if i want to use the same folder i say yes it cheks the files and after it's done i takes me to the screen where backgrounds take over the screen but before i can continue to agree to the terms, the massage above appears, i have no idea of what more i can add i want to know any possible answers, i think i have downloaded all possible things i can and yet can't play PLEASE help me. and am using windows xp

its the same problem i posted a few days ago but it's falling back and think no one will see it, i will still check the other incase anyone answered me on the other one
theres the picture of my problem, at least what i think it is