The reason this happens is because PHP renames the file to a temp file name. The value you want is present in a variable, but I can\'t remember where.
At the end of your upload script put a phpinfo(); call. At the end of the phpinfo info, it will contain all of the variables passed to the script. One of those variables will hold the file name you started with (hello.txt). That is the variable you want to use for $file2;
Hopefully this helps.
You can always see the variables passed to the script by adding the phpinfo() at the end of your page. This is a useful tool for debugging.