Well if you run HyperPi 32MB in a number of threads that equals the one your CPU can handle I would consider it a nice indicator of memory stability. Not that it means your memory is 100% stable but I would say that having a BSOD out of a memory problem gets pretty thin after that. You can also test y-crunsher, for me it showed up as another nice memory/IMC tester. Bother HyperPi/Y-crusher are fast tests as oposed to memtest, though the last will give you a more thorough insight on whether there is/isn't stability problems.