LG TV TO COMPUTER

hey guys i have a little problem with the picture quality of my new tv when i plug my computer into it,
specs
LG LD350 22 inch
connected via hdmi and i have tried vga and dvi with hdmi adaptor all are similar quality,
computer running windows xp pro sp2
intel core 2quad cpu @ 2.66ghz with 3gb ram
graphics card ASUS EAH5770 CU CORE 1GB GDDR5

just need to know how i can fix this the screen is crystal clear on my xbox however as soon as i switch to pc its not right i have it at what i think is the nearest res 1360x768 but i cannot find a my standard screen res or b another prest on that looks better.
please if anyone could help me out i would really appreciate it