first, see Roger's comments. second, to help debug, change your code so it's in the form:

my $file = "\\172.22.1.73\D:\FromC\FitClass\fooo.LOG";
warn $file;
open(REMOTE,'<', $file) or die ("cannot open the remote file '$file': 
+$!");
[download]

Now, take the string from the warn line (let's assume it printed "foo at script.pl line 1234") and try to run start foo from a dos prompt. Does this work? If not, is it because the UNC path is malformed? Note that it could work but your script still doesn't due to permissions issues -- for example if this is being used from a CGI script make sure that the web server (the IIS user account) has permission to read that file.