What would be better/safer tool to shring NTFS partition ?
Any experience anyone here ?

I personally use gparted - it boots as a Live Linux CD and gives you a nice GUI to work with. Very straight-forward and easy to use. I use it to resize the Windows partition when I want to give a machine the ability to dual-boot with Linux...

Good Luck!

Is that for Windows XP or for newer Windows? For newer Windows the easiest and safest tool to shrink NTFS is the disk manager inside Windows.

Even for XP, it is safest to defragment the NTFS inside Windows before shrinking the NTFS with a Linux tool.

Also, it is best to disable the pagefile (virtual memory) in windows before shrinking the partition and reenable afterward.

The UI (parted vs. gparted) matters very little because it does not do the actual work of shrinking the partition. Either parted or gparted would call the same ntfs program to do the actual work.

gparted is just a graphical frontend for parted. One is as safe as the other (since they're the same program doing the actual work). The difference is if YOU, as the end-user, is less safe using a command line program than a graphical based one. That would depend on your experience level. Commandline programs tend to do less hand-holding than graphical programs. But once these two programs get around to the actual disk partitioning steps (past any user interface), they are the same thing.

gparted is a "wrapper" for various tools - libparted and ntfs-3g amongst others.
Most find it more intuitive than parted itself.