A few weeks ago, I encountered a perplexing issue on my Windows 10 desktop that nearly drove me to a full system reinstall. Out of nowhere, my system began freezing intermittently, especially when launching applications like Outlook or when trying to open large Excel files. The mouse would become unresponsive, keyboard shortcuts stopped working, and after around a minute, everything would return to normal-until the next freeze.
Initially, I suspected a RAM or disk issue. I ran Windows Memory Diagnostic, which found no errors, and then used CrystalDiskInfo to check the health of my NVMe SSD-everything was in the green. Next, I tried sfc /scannow and dism /online /cleanup-image /restorehealth to scan and repair possible system file corruptions, but there were no reported issues.
Searching online, I found several suggestions-disabling startup programs, running a clean boot, checking for malware (I used both Defender and Malwarebytes), and even updating all drivers through both Windows Update and the device manufacturer’s site. None of these made a tangible difference.
Things got interesting when I monitored system resources in Task Manager during a freeze. Although CPU and memory usage looked normal, I noticed that “Antimalware Service Executable” would spike right before a freeze. Some threads suggested excluding certain folders from Windows Defender, especially if they contained a large number of files. I added the C:\Users<MyName>\AppData\Local\Microsoft\Outlook and C:\Users<MyName>\AppData\Roaming\Microsoft\Excel folders to Defender’s exclusion list. This helped reduce the frequency of freezes but did not resolve the issue entirely.
The breakthrough came after I checked the Event Viewer logs and saw repeated warnings from the “Disk” source (“The IO operation at logical block address … for Disk … was retried”). Recalling that I had recently connected an older USB external hard drive for some quick file transfers, I unplugged it. From that moment, the freezes stopped entirely. It turns out the failing USB drive was causing timeouts on the Windows disk subsystem, intermittently hanging the OS even when I wasn’t actively accessing the disk.
My takeaway and tip: If you face unexplained freezes, especially after working with external drives, don’t just check your main system drive-disconnect all USB devices, even ones that seem idle. Corrupted or failing peripherals can easily bring a stable Windows system to its knees. This isn’t a commonly suggested troubleshooting step, but it saved me hours of frustration. Hope this helps someone else avoid the wild goose chase I went through.
