How can I create a file of a certain size in Windows XP and later?

A. If you need to create a file of a certain size and the file contents don't matter, you can use the Fsutil command as follows:

fsutil file createnew <name of file> <size in bytes>

For example,

fsutil file createnew d:\temp\1mbfile.txt 1000000

creates a 1MB file named 1mbfile.txt in the d:\temp folder. I've successfully used this command to create a very large file to reduce the amount of free space when I was using a buggy installation program that couldn't address too much free space.

http://www.windowsitpro.com/article/file-systems/how-can-i-create-a-file-of-a-certain-size-in-windows-xp-and-later-