First, you can go to bios and disable "quick boot" or whatever it is called in your bios. This way the bios will test the memory at boot.
If the memory is faulty, it will show already at this stage.
Secondly, to "stress test" you can simply load any of number of test tools available. For example Sisoft Sandra
from:
Sisoftware
Sandra also gives you all other nice info on your computer. Not propaply most reliable test, but enough to stress the memory!