When you have Windows on C:, you do not want to install Linux on C: as well, but D:
If you have put in a scond HD into your PC tower, you may need to alter the booting order in BIOS. At least once you got Linux on D.
Linux will install its own boot manager. This should not overwrite the one of Windows. Because: If you remove Linux, then you have no booting manager for Windows. If however Windows boot manager happened to overwrite the Linux boot manager, you cnanot choose on system booting what OS you want to boot in, since Wndows boot manager does not leave such choice, only the Linux manager allows that.
If you are new to it, why do not test it first like this:
Linux Mint 16
https://www.computersnyou.com/2803/c...ows-linux-mac/
Or Ubunutu:
http://www.ubuntu.com/download/deskt...ick-on-windows
You simply need to google and download an ISO file for Mint 17.3 or 18.
What you get is a bootable USB stick that starts your system in Mint withoutn anything chnage don your HD at all. You can chnage and save working files on stick. You can test it all via stick. Stick needs toget booting priority in your BIOS. If you like it, you can install to hD from within the running Mint stick process, there is a button. But you may want to make sure you colelcted some info on that before youbstart it, regarding partition sizes and locations. Its not difficult, but some initial things simply must be known, there is no way around that.
If your system already is EFIS and not BIOS anymore, google for that, things may be different then, HD installation also works a bit different. I have not done that myself so far, so cannot comment on it by experience.