Possible to mirror files in a folder, but don't delete

Question

Is it possible to have some sort of tool to mirror all files written to a particular folder.

BUT, if that source folder deletes files, leave the mirror folder alone.

Answer 1

Use windows scheduler to run robocopy at a scheduled interval, it will only copy files with newer timestamps and therefore should leave it alone if it gets deleted. Robocopy is built into W7

robocopy "C:\$data" "D:\Backup\$data" /FFT /e /r:0 /w:0

fft - timestamp
e - copies subfolders
r:0 and w:0 will skip over errors

Answer 2

You can use Microsoft's Synctoy, which will do exactly that.