Back up your hard drive now. Or, to be specific get any data off it you can't afford to lose.
The hard drive may or may not be getting ready to go. All current production hard drives have built-in SMART monitoring that constantly reports the hard drive's error rate. Naturally, Windows blithely ignores this information as your drive self-destructs. But you can use third-party software, such as smartmontools, to read the SMART info to see if your drive is on its last legs.
Freezing the laptop may or may not have helped. But you can be confident the problem will return.