Hi Everyone, Before my troubles started I had 2x2gb in riser board A and 2x2gb in riser board B and everything was working fine. However today I came to install 2 new 4gb modules by placing them into slots 1 & 2 of riser B and placing the 4x2gb modules into riser B and now it's all gone horribly wrong! When I turned on my mac the fans went into overdrive but i still managed to get into my account but could only see 8gb of the 16gb installed. I then shut down took out the new 4gb modules put back everything back as before and restarted but this time it powered up but there wasn't even a boot sequence! I've tried switching the boards around and even tried an SMC reset but all to no avail. I'm totally stuck and not sure what to do next can anyone please help?