PC randomly crashing, how can I test it?

A few weeks ago I moved just one floor down as my landlord has been remodeling units in our building. Once I had my PC back up and running, right away I noticed that one of my hard drives no longer would boot. Now as time has passed over the weeks since my system has become randomly unstable. Often while on Facebook, if I follow links to reputable websites that have embedded video such as news outlets, Chrome would lock up or completely shut down. I've also had a similar issue while playing a game on Steam, where it would shut down that game and go back to that game's home screen or completely shut down and I'll be back at the Desktop.

I've already done the usual. Checked the hard drive for errors. Checked for viruses and malware. Cleaned out a lot of old and dead files to free up space. Anything I can think of with 30 years of PC ownership has taught me! I have a VERY important at-home job interview and test that I need to schedule ASAP. How can I stress test my PC to make sure it's stable enough ti won't crash while doing this interview and system testing? I'm not working so I need FREE options!

PC is an older Dell Optiplex 9020 based on an i7-4770. I'm including a screenshot of the system specs. Time is critical!

No, it's a Dell 9020 Optiplex I mentioned...

I'm looking for a stress test of sorts. The CPU is just fine. It's never had any heat issues, and I just cleaned the heatsink.

Check health of the hard drive with CrystalDiskInfo which is a helpful utility that taps into SMART on your HDD/SSD and reports those values back in an easy-to-use interface.

CrystalDiskMark - Crystal Dew World [en]

I'll try that too. Is there any tool out there free or paid that checks CPU, GPU, memory, HDD/SDD, drivers, and Windows? Everything I see on YouTube is for benchmarking not on system stability.

Checkout AIDA64 Extreme.

Downloads | AIDA64