I ran the diagnostic and this is what I got:
Hard drive- dst short test
Error code 0146
Msg: Error code 2000-0146
Msg: unit 0: DST log contains previous errors
error code 0f00:137B
Msg: DVDRW_1- drive media is missing or blank
error code 0f00:0244
msg: Disk_0- block 38006906: uncorrectable data error or media is write protected
error code 0f00:0244
msg: Disk_0- block 38006907: uncorrectable data error or media is write protected
error code 0f00: 1A44
msg: Disk_0- block 38006906: uncorrectable data error or media is write protected
error code 0f00: 1A44
msg: Disk_0- block 38006907: uncorrectable data error or media is write protected
I find that if I shut down and restart my computer it works. As for "(uncheck) Enable 20/40 MHz Coexistence" where would I find this?