Windows True X X

Last ever Windows. Released in ∞E99999999999.

Windows X_X

The startup sound is a very loud, high pitched screeching noise.

The shutdown sound is a brief, screaming, hissing, "Goodwill towards men, I don't think so," and extremely loud, sad, and scary cacophony.

When Windows True X_X crashes, it only shows the error code in red letters on a blank background.

For example, it reads 0x000000F4, which means CRITICAL_OBJECT_TERMINATION.

Source: Windows Xth of X Versions R2 by CromaticTM.