Regarding partitioning a system C: drive and installing Windows 7 on the newly created partition while leaving the Windows Vista installation and files as is where they are; is there a credible risk of messing up the computer by doing that, or is it a safe enough process?
Please advise, thank you.
Nothing is ever safe 
e.g. A short power dip can mess up things.
Create a image of the drive before beginning.
What’s the best program to use for image cloning on Vista Home Premium?
Is it more probably that installing Windows 7 on a partition will go successful or that it will mess the computer?
Hi ehmen!
You should better use an extra hdd instead of creating a new partition. While installing Windows 7 you need internet connection!
After everything you got installed, the boot manager helps you changing between your still existing Vista and Windows 7.
=Snake=
It’s a laptop so I can’t add a HDD.
I don’t know if this laptop has available slots, and I wouldn’t want to open up this very old thing to check.
Is installing a OS on a partition usually successful?
Also, can you suggest the best programs for image cloning in Vista?
Thank you.
Look careful what it says on the screen before clicking ok so you won’t wipe the Vista partition
Opening it would probably be a good thing. It’ll give you a chance to get rid of the dust bunnies. 
Looking up the specs on the manufacturers website will also tell if there is a spare slot.
Since it is a old laptop, likely not.
Does it allow saving a disk image to an external hard drive? (Only CD/DVD and USB are mentioned on their website.)
Isn’t that external HD a USB device ??? If not, how are you connecting it to your system ???
Very long power and IDE cable connected inside the laptop and connected to a hd that is placed on the other side of the room ;D
Really nice, your fantasy.