Hello, so my friend gave another person his 512MB RAM DDR which I believe is 400Hz or something of the sort.
The person's computer has in total 4 memory slots, 2 being used with two 256MB RAM sticks and the other 2 free.
So we took off the cover, completely powered off the computer by unplugging and everything and inserted the 512MB stick into the free slot.
Then we turned on the computer and we heard a few beeps at the beginning, and just a black screen saying "no signal". We said ok, no biggie, that must mean that it's just incompatible. So for a last try, we tried putting the 512MB stick into the other free slot, after that, screen appeared but quite f***ed up looking and some quick text appeared "memory failure... blablaa more text".
We turned off the computer, took off the 512MB stick and powered the computer on again hoping that everything will work as normal since we took off the incompatible stick but it just kept on saying "no signal" on his monitor and there was some weird popping noise coming from his computer ever since.
We have no idea what just happened and what to do. If someone here knows what the problem is and how to solve it without buying anything new that would be great, I don't feel like paying for that guy's repair..