You can use fsutil command to quickly create large file in MS Windows. However, this command requires administrative privilege. Here are some examples showing how to create a 1 kilobyte file, a 1 megabyte file and a 1 gigabyte file.
REM Create 1 KB file. fsutil file createNew myBigFile-1KB.txt 1024 REM Create 1 MB file. fsutil file createNew myBigFile-1MB.txt 1048576 REM Create 1 GB file. fsutil file createNew myBigFile-1GB.txt 1073741824