Hardware diagnostics software

Is there generic software on the market that you can run to test for hardware failures on a computer? My PC has had almost everypart replaced and I am ready to throw it away except that I’m thinking that I literally have a different computer (and operating system) but the same problem. I sent it to the shop and they replaced the motherboard, powersupply, hard drive and operating system . The PC worked for a month or so and the symptoms reappeared … either reboots by itself, freezes or doesn’t boot up at all. I have also replaced the video card, swapped the monitor, added an UPS, and changed out the memory. Chkdsk finds a bad block. Please help this fool.