Computer doesn't shut down when in standby mode.

Several types of standby modes exist. The basic S1 mode shuts off all components while the computer keeps making noise, being in a semi-standby mode. In the S3 mode, the computer appears to be turned off, but is actually in a standby mode. You may choose which of them you want to use in the BIOS system – in Power Management, choose S3/STR or S1/POS.