are you required to unblock a file for it work properly?

[cov3rt]

i just want to know if its required for you to check the option for file properties to unblock it, for it function properly? reason why is ask in particular is because i downloaded an iso to create a custom windows image, but i noticed right after i created the new image, the original iso file had the unblock option, and i didnt "unblock" it. would there be any issues with my new custom made iso file? 

[UCyborg]

No. Blocking in this case is just some extra metadata attached to the file entry in the file system using NTFS Alternate Data Streams. I've yet to encounter a program that would make a fuss about it. Windows gives a warning if you try to run executable program blocked this way.

Using some kind of download manager tends to prevent the file being blocked on download, at least the following two. I use DownThemAll! - XUL extension for older Firefox and derivatives that kept support for these types of extensions. My main reason for using such download manager is ability to preserve file last modification timestamp. More universal download manager when it comes to browser support is Internet Download Manager.

[Connor McMahon]

No. This happens to me a lot in Vista though.