I don't understand that as well!
No Ulco, I'm running 64bit Win7 on my machine, and last year I bought 8GB RAM for my computer (two 4GB modules). Put it in, nothing happened. The computer didn't even start. Brought them back, got four 2GB modules. Put it in, nothing happened. The computer didn't even start. Tried to put in only 4GB. Nothing happened. The computer didn't even start.
Drove back to the shop, killed the guy who said it should work, got arrested, went to prison, broke jail, came home and put in my 3GB again, cried a bit and accepted my situation. Till now.