[Remix OS for PC] :
!!!QUAD Boot Windows/RemixOS/CM13/Android 7!!!

Read ahead if you want to

I am unable to install this version as well. Official ISO worked fine for me 64bit. It's pretty easy to do this yourself using the Xposed files from the OP's ISO file or a few posts back Moman2000 was nice enough to post the Xposed files.

Install RemixOS normally using installer. Using RMXtool 1.8fix, extract the system.sfs into an img file. Then extract the system.img to it's folder. Root it using rmxtools. Put the Xposed folder into the extracted system folder. Go into the xtracted system folder and copy and past everything from within the Xposed folder into the extracted system folder as well. Accept overwriting the files. Pack it back into a system.img file using rmxtools. Dont forget to input the size you want the system.img file to be. Now throw that freshly made system.img file into your installed remixos folder. Delete the system.sfs file as you dont need it. I was surprised to find that the uncompressed system.img ran fine as is. Correct me if i'm wrong but i also read that you cant have a .sfs file with R/W access to it. So as an .img file R/W access is possible. I then used the initrd-3.0.207-x64 file that was graciously posted and overwrote the one installed into my remixos folder. Using the OP's instructions I then mounted my EFI partition in windows and edited my grub.cfg file. I added the RemountRW option along with the DEBUG option since i wanted to install Xposed. Since I'm on windows 10x64 and using a efi bios changes only stick using that particular file. On a side not I had alot of fun and was able to tweak that file to show whatever i wanted at boot. For instance i changed Windows to Windows 10. I got rid of the the little icons next to remixos and remixos advanced. I renamed remixos advanced to CM13 :D. While still in the EFI partition I went to boot folder and copied the remixos folder, renamed it cm13 and stuck that in the boot folder as well. So when i was done i had the Microsoft folder, remixos folder and copied and renamed CM13 folder. I also tweaked the locations in the grub.cfg file in the remixos advanced heading. instead of pointing them to my remixos folder on my C:/ drive, I pointed the Kernel and such to CM13 instead:D. I also added the RemountRW and DEBUG option to that as well. Done with the grub.cfg file, I then Went to C:/ and created a CM13 folder. I then downloaded the CM13 iso from the androidx86 website. Extract the iso and throw those files into your newly created CM13 folder in C:/. So when your done you should have a CM13 and remixos folder in the root of your C:/ drive. Repeat the process of using rmxtools to extract the system.sfs file of cm13 to system.img. Extract the system.img to a folder. repeat steps above like you did with remixos. Pack it back into a system.img file and put it into your CM13 folder, then deleting the original system.sfs. Using rmxtools create any size data.img you want and throw that into your CM13 folder. You can make one and put it in your remixos folder as well if youd like. It should save some boot time:D. Also dont forget to overwrite the initrd-3.0.207-x64 file in your CM13 folder. The same file works for both remixos and CM13 as does the Kernel. Now go ahead and reboot your rig. Hopefully upon reboot you will have Triple/Quad boot options like i did. I can boot windows, remix, cm13 or Android 7. Both remixos and cm13 with full RW access, SuperSU, and fully working Xposed. Upon your first boot use the OP's intructions to install xposed using the terminal commands. When you are done installing xposed in remixos and cm13 you can again edit the grub.cfg file to remove the DEBUG option. Enjoy your triple boot. I was unable to get the newest androidx86_64-6.0R1.iso to boot. I was also unable to get the androidx86_645.1.img to boot using this method. If anyone knows why i'd love to understand it. CM13 runs great though as does remixos. I also along the way found out that all of my previous booting issues were caused by my AMD R9 390x video card. I had to revert to using my onboard intel HD4600 from my 4790k. Installed to my ssd android screams. the only issue I have now is that showbox keeps crashing. if anyone knows a fix for that i would love to hear it. Enjoy guys, hopefully my exhausting few days of messing with all the various androidx86 stuff helps somebody out. If you want to quad boot Android 7, repeat the step used for CM13

Tidbit 1- I think using Titanium Backup i froze or deleted Home and was able to use a 3rd party launcher with 0 issues and with taskbar intact

Tidbit 2- Android 7 ran great as well but no Xposed support for that version

Tidbit 3- First thing you always want to do is DISABLE ROTATION, enable developer options, allow root, update or install superSU.

Tidbit 4- I found the Android 7(Nougat) iso floating around somewhere from the androidx86 guys

Tidbit 5- While using notepad to navigate your mounted EFI partition you have to select show all files instead of show txt to create any xtra folders for triple or quad boot