That amount of ram is pretty bare bones for Windows Vista home premium.
Also it says that the video is up to 256MG shared memory which is taking some of the 1 gig.
I have a HP with Vista home premium and the difference in speed between the 2 gig compaired to 1 gig was very noticeable.
old pc: Compaq Presario w/ Windows ME, celeron processor, 316ram
new pc: HP Pavillion dv6425us w/Vista Home Premium, Intel Core 2Duo processor T5200 (1.6ghz) 1024mb DDR2 SDRAM 2dimm, 5400rpm hard drive.
PROBLEM-- new pc is much slower than old one!!!! Do I need more RAM?
How much? Should I take pc back and get another? (I just got it 4-5 days ago, not even hooked up to internet yet) Help please. Thx,wsh

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic