How do I synchronise two folders in real-time in Windows 7?

I want to synchronise two folders in real time under Windows 7.

Basically, I want to monitor a folder and synchronise each change (new files, changed files, deleted files) to another drive. It has to be in real time, so it gets synchronised instantly when a change happens. A one-direction synchronisation is enough.

I tried Microsoft's SyncToy, but it does only syncing by hand or scheduled (thus not satisfying the "real-time" requirement).

Can this be achieved with Windows 7 itself? If not, are there other methods of doing this?

Dsynchronize lets you do this. I'm not sure how it works in Windows 7 but it's freeware and standalone so there's no harm in trying.

I use the ROBOCOPY command and made a command line to do the sync between two folders (incremental sync).  My command is like this

ROBOCOPY "Source_Folder" "Destination_Folder" /E /ZB /XJ /XF "~*.*" "*~.*" "desktop.ini" "Thumbs.db" "*.torrent" ".lock" ".Sync*" /xd "Rubbish" ".Sync*" ".Box Sync" "_private" "Outlook Files" /FFT /MT /R:2 /W:5 /V /MON:1 /TEE

(exclude files: "~*.*", "*~.*", "desktop.ini", "Thumbs.db", "*.torrent", ".lock", and ".Sync*") (exclude folders including files in these folders: "Rubbish", ".Sync*", ".Box Sync", "_private", and "Outlook Files").  Also this repeats itself every minute and/or single change of file/folder.

FLAGS

/E      Copy subdirectories, including empty ones.
/ZB     Use restartable mode; if access denied use backup mode.
/XJ     Exclude junction points. (normally included by default).
/FFT    Assume FAT file times (2-second granularity).
/MT     Do multi-threaded copies with 8 threads.
/R:2    Number of retries on failed copies.
/W:5    Wait time between retries.
/V      Produce verbose output, showing skipped files.
/TEE    Output to console window, as well as the log file.
/MON:1  Monitor source; run again when more than 1 change seen.

/XF [files]  Exclude files matching given names/paths/wildcards.
/XD [dirs]   Exclude directories matching given names/paths.

For the list of flags, please refer to The Ultimate Guide to Robocopy.

There's Synkron which is open source and is cross platform.

You could use a NTFS Symbolic Link so that the folders on each drive actually point to the same folder.