From the ST8 Solid Edge readme file (attached):
Windows 10 is scheduled to release in late 2015 after Solid Edge ST8 is released. We will test ST8 on Windows 10 and plan to announce support of Windows 10 with Internet Explorer 11 in ST9 and in an ST8 Maintenance Pack after testing is completed and any critical issues are resolved. Solid Edge will not support the new Windows 10 browser, Microsoft Edge (codenamed Spartan).
So to answer your question, at this time ST8 is currently *not* supported on Windows 10.
Successfully installing software and successfully running software are not the same thing. Just because you may be able to get ST1 installed, does not meant that ST1 will run. Given that you are looking at approximately 8 years time difference between ST1 and ST8, the chances of ST1 successfully running on Windows 10 would be slim.
If you really need to run ST1, then IMHO you would be better served building a virtual machine to run inside in your Windows 10 system, and then running ST1 on the virtual machine.
Also, an ST8 license is *not* compatible with ST1. In order to license ST1 you will need an ST3 or earlier license file.