(1) PC sometimes will not boot up. It gets stuck as the the BIOS boot screen:

(2) Other times it gets stuck after detecting RAM and CPU:

(3) During boot up sometimes the PC hangs, with dots are lines on the screen:

(4) A few times the PC has crashed during boot with this screen. Note the white line appearing - which I have circled in red:

(5) Memory errors.

When Windows Vista crashed with a STOP error. I reboot and run MemTest86. This now shows memory errors:

(6) An other Windows STOP BSOD. I reboot and run Memtest86. I get memory errors: