I installed 2gb ram on my vista core2 dou 2 ghz. win= installed ram is 2GB but physical ram is only 1GB...help?

my acer aspire 5580 is win vista 1GB. when i open any picture using windows photo=blacks out. so i removed the 512 x2 ram and installed 2Gb x1 ram. ms32info says installed is 2GB but physical ram is 1GB. any thing wrong ?. i checked bios info= says 2gb ram, but belarc reports 1gb available.