thonayan99:

you could try to do the following:
get md5sum - that's just a very small .exe, no installation.
run this with both files in the same location:
this should give you exactly this output:
if the long number/letter combination at the beginning is any different than the one here, your download has errors and you can try redownloading.
actually, this string is in the file "MD5SUM" on http://tablets-dev.nokia.com/nokia_N900.php, i assume these files are the same for everyone.

if the string is exactly the same, i would say that your hardware has a fault, and you should return it to nokia...