While searching for the issue, I first found a webpage that had someone with your exact problem... It Is Here
In that post is a link to (one of) the supposed solutions to the shelliconhiddenfile or whatever its called
its found Here
Chances are you have that same program and unisntalling reinstallling it may help, If you do not have that program and those instructions do not help, Ill have to do some further digging..
How much RAM did you have prior to install is it 1.5 prior? If so how much more did you put in, if you put too much in, which isn't a problem , THen windows may actually just recognize 1.5 gigs while the rest is there, But invisible...
I know usasma has stated multiple times he has 4 gigs in his system and it only actually identifies 3.25 of it or something around there so it may just be there, But windows doesnt' recognize that much
Redoing your name Im not sure how to do that, I know that its probably under the control panel system function but Im not 100% so Ill let someone else answer that
as far as how much memory windows says it has, You can find that by going Start Control panel, System and under general tab it should say "COMPUTER:" and it will say how much ram it sees, And how fast your processor is etc..