A failing memtest is a strong indication that something is wrong with your memory. At least one of your memory sticks seems to be faulty. If you have multiple RAM sticks in your system, you could try removing one and rerun the memtest and see if it passes. If it does pass, then the stick that you removed must have been the faulty one. You could then either proceed to run your system without the faulty RAM stick and just deal with the fact that you have less memory, or you could buy a new memory stick as a replacement.