Last part first. Ubuntu is only one of the many varieties of Linux, and seems to be gaining greatly in terms of popularity. I and many of my friends use it as their operating system of choice.
Also the range of programmes is immense although if you're looking for direct replacements for Windows programmes you may sometimes have a little difficulty.
If you're anything like me you will find it a little different at first with a bit of a learning curve, although it is worth the effort.
I've tried it in many ways, including Grub and both systems on one disc, but the system I'm using on this computer, the one on which I'm typing, is to have Win XP on one disc and Ubuntu on another. That way the one system doesn't affect the other and a choice of which to select is made at boot time by choosing the appropriate disc.
Another of my computers has Ubuntu as the main system with XP running inside a programme called Virtual Box.
I haven't encountered Linux 7.1 pro but it can't hurt to try it, although I would suggest that if it is an old system, as you imply, then you could have difficulty with some drivers. I might just be worth downloading the iso of a newer system that could then avoid such problems.
Best of luck with your trials and I hope you enjoy them