Firstly, do you overclock? If so, return settings to stock.
Secondly, if you have more than 1 stick of memory, remove all but 1 stick and run Windows memtest to see if you get any errors. If errors appear quickly using stock settings then you either have a faulty memory stick or a faulty DIMM slot (so remember to try a different slot to see if the errors disappear). Repeat the process with each memory stick.
Finally, if you don't get errors with individual sticks, put them all back in and test again. Using this method, you should be able to find the cause of the problem - either a bad stick or a damaged slot.