When the opportunity to upgrade from 7 to 10 was presented, I was dubious, because I did not know if I would get all drivers and compatibility with all the software I had installed. (it turns out I was right, because I can't get a win 10 driver for my on-board Radeon 3000 graphics processor) Anyway, I decided to resolve the issue by using two hard drives, upgrading win7 to 10 on one and installing a fresh copy of Win 7 on the other. It worked fine and I had a dual boot start-up which offered Win 7 as the first (default) option. I had previously had a dual boot system on my older computer, with XP an 7 on, because I had software and hardware (Soundblaster Live Drive) which didn't work with Win 7 64 bit. Unfortunately, Win 10 is on disk 0 and Win 7 is on Disk 1 and, although I reinstalled Win 7 from the installation disk by booting from CD, there was no Boot Manager installed on the Win 7 drive. Consequently, although when I boot to win 7, windows explore sees the Win 7 partition as C and Win 10 partition as F, if I try to download and install new software, it wants to install on F. I believe the system sees the Boot drive (Win 10) as C and the Win 7 drive as something else, probably F. I could accept this and trust that the installation was going onto my Win 7 drive, but if any program referred to application extensions or subroutines prefixed by F:\, when the run on my Win 7 disk they won't find what they're looking for. I want to build a new boot manger on my Win 7 disk and swap the SATA connection so that it is disk 0. I am nervous of making mistakes rendering the system unbootable and having to start it all again from scratch. Any and all advice will be appreciated.