How spooky - I just found the guts to upgrade from Win7 to Win10
I was running out of room on my 250gb SSD so upgraded to a 500gb SSD (Samsun Evo 850, which is great value & performance)
Her is my experience and the few wobble - but everything seems to have ended up well
First of all I cloned by existing C drive (with the win7 OS on it) to a new hard drive (connected via USB) using Macrium Reflect - a free utility that did an amazing job, even copying the hidden "restore" partition on my original hard drive
I then installed the new hard drive and made sure everything worked in Win7
I then upgraded to Win10 on the new hard drive (safe in the knowledge that if anything went wrong I could put the original hard drive back in and be where I started so it is a huge safety net to have - but as an added precaution I also created a disk image of my drives onto a separate external hard drive)
Everything went smoothly and here is a list of the "wobbles":
After installing the new hard drive Windows only saw it as the size of the old drive. This was easily overcome by "expanding the partition" in Disk Management so Windows now sees the whole drive
I needed to "re-authorise" my IK plugins (Amplitube etc.) as I was getting a regular "static sound" - this was easily done using IK's authorisation manager. I also needed to do the same for Addictive Drums 2, but this was also very easy
All other plugins (Waves, KOMPLETE Ultimate 10, Sonar etc. we're all fine and didn't need any attention at all)
The only other issue I had was that Win10 does not support the "KeepSafe" fingerprint protected folder I had on my hard drive - so I simply popped the old hard drive in, copied out the files I needed (as the PC was exactly as it was before the upgrade) and then went back to the new hard drive
I am very happy with the result and it is nice to know I am all "up to date"
I would say go for it but buy a new hard drive if you are using your PC for paid music work (as I am) because you can always get back to where you started by putting the original drive back in