Is It Safe to Force Restart a Computer?
Generally yes, as a last resort when a computer is genuinely unresponsive — but it's not risk-free. The main danger is interrupting something mid-write, such as a Windows update or a file being saved, which can occasionally cause further problems.
When it's reasonably safe
If the computer is frozen with no response to anything, and you're not aware of an update or file save actively in progress, a forced restart (holding the power button) is a reasonable step and won't usually cause additional harm.
When to avoid it
Avoid forcing a restart if you know a Windows update is actively installing, or if there's visible drive activity suggesting something is being written — interrupting these is one of the more common ways a minor issue turns into a bigger one.