Is your primary machine Windows 8.1 or Windows 10?
What is your graphics adapter (AMD/Intel/Nvidia)?
So after spacedesk installation, your PC becomes problematic?
Is your primary monitor shows black screen after spacedesk installation?
For further analysis, could you please send us the following:
- run dxdiag.exe on your primary machine, click "Save all information" and send us the output file (dxdiag.txt)
- spacedeskSetup.log file located in C:\Users\Public
Please save all requested files in one folder, then right-click -> Send to -> Compressed (zipped) folder, then attach the *.zip file on your next reply.
PS: Attach option should be visible on your side after your second post.
By the way, We have merged your other post here.