Curious: what happened to memory?

[cookydeacon]

Curiosity: I have 2 DDR3 Ram sticks @2GB each. Current memory read shows only 3GB total; one at 1024 and the other at 2048. What happened to the other 1024 on slot 1? PC is 5yrs old; windows 7 using an AMD processor. I am going to replace within year, so will probably just replace one sot. Does it have to be identical? Coincidently, I notice the L2 cache @1024

 

[Emerald]

Is it a 32-bit version of Windows7?

 

[cookydeacon]

Is it a 32-bit version of Windows7?

 

[cookydeacon]

Thank you. It is a 64-bit.