Installing a Video Card decreased computer RAM?

My computer is running Windows Vista 32 bit. I normally have 3 GB of RAM, but that was when I had my old video card. (Was an integrated Intel GMA 3100.) Just yesterday I upgraded my power supply from 250 watts to 500 watts, and I installed a new video card, a 1GB GDDR3 ATI Radeon HD 5570. However, after installation, I noticed that my computer RAM had decreased from 3 GB to only 2 GB. What happened, and is there any way to fix it back to being 3 GB?