System restore only do what it's supposed to do... recover a
system from disaster, especially after a disastrous update... it
doesn't help if your system is infected.
Because... the files are on your PC.
But the core of Windows is the registry. Doing system restore
may restore the clean registry back... but whether it removes the
files... I'm not so sure. By the way, I'm not a fan of system
restore, although it is useful when it comes to forensics
investigation.
I'm not a fan too... But the last time I tried for fun on my
comp, files that are created after restore point date actually
disappeared. But for my friend, her files didn't disappear. Till
now I've no idea why.
But in my friend's case, the spyware was gone.