How safe is it to install Ubuntu on a Windows 7 PC - repartitioning the disk?
If there's data you can't stand to lose (ie that couldn't be recovered by just reinstalling) it doesn't matter if you're repartitioning or not, back it all up to an external drive.
Resizing NTFS is a pretty tried and tested technology (it has been one of the main install vectors for people trying Linux in the past, and probably still is) so you should be fairly confident you won't rinse your drive when you do it. It's had a lot of attention and there are a lot of tools out there to simplify the process.
That said, none of them come with any warranty to work or against data loss. But, as I say, you can minimise any loss by just taking a backup.
You can use something like CloneZilla to make the initial backup to an external drive. I think it also supports network locations too so you have options available if you can't clone to an external USB disk.
For some reason, I don't trust linux tools dealing with NTFS because of a lot of bad experiences. Windows comes with a good disk management tool for FAT/NTFS, and I'd say that's your best bet. I've done this for a lot of people I've initiated into Ubuntu, and it's never failed.
- Boot into Windows
- Press start+r to open run
- Open
compmgmt.msc - Select Disk Management > Local (snap-in)
- Right-click the bar representing your C: partition, and hit shrink volume
- Wait a while as it queries available space [should be enough]
- Tell it how much you want to shrink by
- It should leave a black unallocated segment for you to do anything with.
You should now has as much free space as you asked for; do what you want with it =)