This trick is just used to create a file which contains no data but of any size you want it to be.
First you will have to convert the size of the file in to hexadecimal notation.
For example, if you want to create a file of size 2000bytes, then convert it into hexadecimal. Use the windows calculator in the scientific calculator mode to convert 2000 bytes in to hexadecimal number.
2000 converted to hexadecimal number will give 7D0.
Now open the command prompt(run > cmd).
Navigate to the folder where you want to create the file.
Input the command debug filename.extension and hit enter. (Do not use the file name of any of the files in that directory)
You will obviously get a file not found error, just ignore it.
The filename can be any file name and you can give any extension you like. Note that there is a space between debug and the filename.
In our case the hexadecimal number was 7D0, now put zeros in front of it in such a way that finally the hexadecimal number consists of 8 digits.
That is 000007D0.
Now, enter rcx in the command prompt after debug command and hit enter.
You will get a prompt with a colon.
Now enter the last four digits of the hexadecimal number we have got.
That is 07D0 and hit enter.
Now type rbx and then hit enter.
Now type the first four hexadeximal numbers at the colon prompt.
That is 0000 in our case.
Now type w and hit enter to write the file of 2000 bytes.
Type q and then hit enter to quit the file.
Use this technique to create any file of any size you need. Note that the file will not contain any kind of data, just junk.