Bob is having problems with his computer becoming unresponsive. It suddenly freezes up until he reboots it. Leo says that it may not be crashing for freezing at all. It may be an unresponsive mouse or keyboard. If the clock continues ticking, then it hasn't crashed. But if the clock is stuck, then the processor has halted. Even then, the processor may just be busy and he may just have to wait. He'll want to be sure it's really halted, though. If he reboots the computer in the middle of reindexing the hard drive, it could corrupt his drive. So he should just go grab a cup of coffee and then see what happens. If it's still frozen, then he'll need to move on to the next step.
It could be bad software, hardware, or heat. It's almost always a hardware issue though at that point. Leo suspects that it may be overheating. It could also be his hard drive. It may be time to back up the data, wipe the hard drive, and reinstall Windows. Leo says though that it's likely a flakey hard drive with signs of failing. Hard drives are cheap, so he can just replace it. He can also update his motherboard's BIOS. Sometimes that fixes everything. Windows 10 has a nice recovery that will get him back to a fresh state. This is also a good reason to make sure he has a backup, especially one that's off-site.