A scream played through my PC at night. Could it be malware?

Weird audio alone doesn't establish that the PC is infected. A browser tab, background video, game, chat app, or notification could be responsible. The timing by itself doesn't tell you whether someone was targeting you.

If it happens again, check the Windows volume mixer to see which app is producing sound. You can also close apps one at a time and check for open tabs or media playing in the background. Keep the volume low while investigating.

Start with a full Windows Security scan, then run Microsoft Defender Offline scan. The offline scan restarts the PC, so save your work first. You can also run an updated scan with another reputable security tool if you want a second check.

A clean scan is reassuring, but it doesn't prove the machine is clean. If the scans find something, follow the removal guidance and check whether the detection returns.

The unfamiliar sessions are worth checking separately from the scream. Location labels can be approximate, so an unfamiliar location isn't proof of an intruder, but sign out any sessions you don't recognize.

Change the chat account password from a trusted device, enable two-factor authentication, and check the recovery email and other security settings. Do the same for your email and any other accounts that reused that password.

If you find signs of an infection that you can't confidently remove, a fresh Windows installation is the more thorough option. Back up your important documents first, then reinstall from trusted installation media. Be careful about restoring old programs or files that might have caused the problem.

I wouldn't wipe the computer solely because of one unexplained sound, though. Check the app and account activity first unless you find stronger evidence of compromise.