I have sonar x3 installed on a Lenovo yoga pro 2 with windows 8.1. Upgraded to windows 10 but could not get sonar to open. I tried to reinstall sonar after the windows update, but the sonar install does not seem to complete. As a result, I had to roll back to 8.1, and now Sonar x3 opens fine. My question is, do I need to purchase another full version of Sonar (Artist) to use windows 10 or is there a way to use x3 with 10 that I am not seeing?

I am currently using X3e on Windows 10 without any difficulty. I do not have Windows connected to the net (don't like forced updates, plus I don't like Microsoft getting all my stuff anyway). This also allowed me to turn off stuff (like firewall and network adapters) that I didn't need running in the background. So it is possible to run SOnar X3 and Windows 10 together.
 
Does anything work, or does it just not come up at all when you try to start it?

Did you run the Sonar install as "Administrator"?   I recall having problems installing a version of Sonar because I wasn't running the install as Administrator.  I restarted running as Administrator, and it installed without problems.
 
If it works on 8.1, it WILL work on Win 10.  Win 10 is basically "Win 8.1 improved".  Same drivers, etc., as 8.1.
 
I have Platinum, but when I upgraded from 8.1 to 10 (on two different PC's) both worked after the upgrade.  I did have to reauthorize Addictive Drums 2 but that was all.
 
I always disable the NIC (Ethernet) when I run Sonar.  Have done that since Sonar 7 and Vista.

It did not come up at all.

Will try to install as administrator next. Thanks.

I've not had too many problems with Windows-10 and no sort of problems with Sonar arising from Windows-10, however the forced updates scare me. I have had to roll two of them back. The last update removed an unrelated program and while looking into it I found that my antivirus had been disabled by W-10 since the end of September. I got a message telling me that Norton 360 is not compatible with "this version of Windows". Once I rolled back I uninstalled Norton and re-installed it. IT works again now... so, while no Sonar problems, I fear that these constant updates that come whether we want them or not are sooner or later going to really mess things up. PCs are configured too many different ways with too many different devices for this. Sooner or later it is going to cause something really bad. The NVIDIA cards not working was a hint.
I'll switch my DAW over before the "Free" upgrade offer ends but I still worries me. I'll do a drive image first.
I keep hoping that MS will rethink this policy and let us decide when and if to update Windows.
I found the message on the last one to be offensive. The first thing on the screen was "WE HAVE UPDATED YOUR COMPUTER" thee next message was "YOUR DOCUMENTS AND FILES ARE RIGHT WHERE YOU LEFT THEM" (I think that is what it said, it was close to that)... BTW, they weren't. I got so mad I was ready to move to a MacBook but I've calmed down and really, I don't want to but if MS keeps pushing my buttons and stick poking me I will. I prefer to decide what is best for me and make my own mistakes.
Anyway, as I said... for me, no problems with Sonar but certainly problems... however, I think the gains outweigh the problems. It is faster and Sonar is faster. You can keep an eye out for things over on tenforums. They are very helpful there too.
J