Did you change or add anything to your box before these errors showed up?
When do these lockups occur. Is it looping sound, blue screen or restarts?
First, memtest86 should be used to illuminate any memory errors.
Is the SMART status of your hard drive in the green?
My current favourite random diagnosis on no info whatsoever is the PSU. How old and what brand... what do you have in your box in its entirety?