The ram and the CPU are independent of each other. Hyperthreading does not care about the type or amount of ram you have.
A dual core cpu will show as 4 cores in the device manager if HT is on. This is because each core can do 2 threads at once, so the operating system treats it the same as a 4 core CPU.
"Control panel" then "system" should show you how much ram you have.