Hello! I've been dealing with an interesting brand of PC freezes on an old PC. What happens is that occasionally the PC slows down to a crawl (you can move the mouse around, but clicking/ pressing keys does nothing), as if it's waiting on something to happen, and after a while it freezes, and has to be reset. Now, after a reset, the BIOS won't see the system disc during disc check (it will wait for a while, and then simply load the remaining 3 data HDDs). It usually helps to turn the PC off (holding down the power button - that way the disc detection goes normally after starting up again). The specs are these: MB: Gigabyte GA-Z68P-DS3 (rev 1.0, latest BIOS) CPU: Intel i5 2500k (normally OC to 4,3GHz, problem prevails even at stock "fail-safe" settings) RAM: 8Gb DDR 3 @ 1333 (XMP profile is off) GPU: Gigabyte Nvidia GTX 970 (no OC) Windows 10 (latest official release, no previews) on an Intel 520 180 Gb SSD (latest firmware - version 400i) I have thought at first, that the SSD was failing, but the current Intel Toolbox diagnostics software for this SSD said (after a full check) that the SSD is in good condition, and that it didn't detect any faulty sectors, or r/w issues. It did freeze once when I tried to run the Windows disc check yesterday (through file manager) - it slowed to a crawl and became unresponsive immediately after I've started the test. I also performed the Windows integrity check through command line (sfc /scannow) - it found and repaired some corrupt files - and after completing the test it also did the same freeze. After getting to Windows again, I performed both tests again, but this time they ran fine with no issues, and the PC worked after that. I also reinstalled Nvidia drivers (in safe mode and with the help of DDU). Can anyone offer any idea on what may be happening? It wouldn't surprise me if some other part was failing (CPU/MB/RAM are all old parts that have been in daily use since day one), but it's hard to pinpoint the issue.