You, Sir, are an easy target for extortion... Nothing guarantees you that the 'commercial' product you're going to buy doesn't mess your data. 'Oh but's it's commercial, it's someone we can sue if something goes wrong', no, if you read their EULAs, you're on your own.
And it's not freeware, it's opensource, like Linux, FreeBSD, WebKit or MacFuse.. Webkit? That's what Apple uses for Safari... FreeBSD? That's what Apple uses for Darwin, the backbone of OSX... MacFuse? Where did I hear this name before? Oh, I know, it's what PARALLELS DESKTOP FOR MAC uses to write to NTFS (Windows partitions).
And if you're so concerned that you'll lose your data you can clone your NTFS partition first using Winclone, oh, wait, it's free also it can't be trusted...
Look, Gparted (and Winclone) have been used reliably by thousands of users including me that can atest for their reliability.
It's your loss, it's your 100, the fool and his money are easily (G)parted.
Besides, you should specify here that if this is a Boot Camp partition or a virtual hd.
If it is a Boot Camp partition resizing it is tricky because very little software out there can resize HFS+ (OSX). It's easier to backup the partition (using something like winclone), delete the partition in OSX, and create a new one with Boot Camp Assistant, then restore to the new one.
If it's a virtual one, you can just bloody clone the machine first for safety and then use whichever tool that does parting, if anything goes wrong you always have the backup.
Safety and Security is not something you trust blindly, it's something you achieve, in terms of partition resizing you achieve that by backing up first, not by throwing money at it.
But I'll shut up now, and let others suggest you the extortionware you are eager to pay.
But chances are that the more technical savvy users will feel gparted is perfectly up to the task, only the less technical ones will suggest what you want to hear but those ones likely blindly bought a resizing product that happened to work once and will swear by its reliability. Any partition solution is likely to work since it's not exactly rocket science.
Last edited: Nov 19, 2008