With LLVM and silverlight this may be possible now (or it may be possible with flash).
I like the user to select a file and then do the following things
1) Hash it with md5 and sha1
2) If archive check if an exe is in it
3) If archive check if password protected
The first to see if the user has uploaded it already (today, yesterday, last month)
2nd to prevent viruses
3rd i should be fine without but if i decide to not allow protected archives i can warn before the user uploads it.
How may i do this through the browser?
You can do this across lots of platforms with Java or Flash.
If you only care about doing it on Windows you can do it with those 2 or Silverlight, an embedded WPF page, an embedded Windows Forms page or an ActiveX control.