Far as I recall the 660 states it supports up to 8Gb Ram. I placed an extra 4Gb in mine bringing it up to 6 and it works fine. Perhaps swapping the modules around or try running laptop with just the new RAM first. mind you I imagine you would most likely have tried this already. Failing which, it is entirely possible you may have a dud Dimm. Updating the bios which hasn't been changed for ages cos the 660 is an old model may or may not make a difference depending on how old your current bios is. As a footnote to this, always read what bios improvements/changes are listed in the readme accompanying the bios. So don't update the bios for the sake of it as although bioses and the procedure to update them are far more stable today than they ever have been you can still screw things up if you don't know what you are doing. Luckily, so far I've never messed up a bios in the 25 years of working with PC's but it can happen to the best of us.

There are so many reasons why any pc won't boot and I think it is fair to say that the question requires more detail before it can be answered properly.