/dev/urandom saves my day

Hi guys,
It has been a long time since I have last posted something on my blog, I have been very busy with my senior year and have not been able to post anything due to upcoming exams that happen almost every other week, but I have still be reading and researching on security stuff.
Anyway, I have been recently researching on password recovering and for those who don't know I have created a collection of password recovery related scripts in perl on google code http://code.google.com/p/kalgecin feel free to checkout the svn.
I have been downloading ophcrack vista live cd on my friends internet that is fast. Well we reached 99.8% and the power went off, withit the internet and others.Well I mounted the .iso on /mnt and performed md5 checksum on the files. I showed several IO errors because the image was not complete and the table3.index did not match the checksum. Damn it, so I decided to eliminate the IO error by using dd to add some bytes to the .iso so that the memory of the iso will match the memory of the image. I performed the checksums again, this time without any IO errors and WOW the table3.index showed OK! I tried doing the same again just to see if it were the random bits that completed the checksum or just the memory space, but couldn't get the checksum right again.
Well that shows that i was just lucky that time. But I still did finish the download on my VERY slow internet that is at most 3KB/s and all the checksums fell into place.