Games arent runnign right

I tried this on hardware but no luck im hoping guys that game would know what a hardware problem or software im having.This is what i cant figure out!I play half life 2 with 150-200 fps on HDR full settings! I cant play battlefield 2on high well maxed out on single player but cant even play it on low on multiplayer. I kinda figured out im not having lag from the game or server Im thinking something is wrong with something with 1 piece of my hardware that windows xp my not like.Im wondering if i bought this pc hardware to soon before vista came out.I have a 2nd system that i poured my soul into ''about 1700 bucks").I bought one of the best asus a8n sli boards for like $229,2.5 gbs for $300 kingston,7800 gt bfg tech $300,$130 500 antec smartpower 2.0.I have more crap that added up like monitors and sound cards and dvd burners/harddrives.


This system did amazing on bf2,bf2142,half life2,rainbow six vegas,even splinter cell DA maxed out! I just cant figure out y this monster of a computer ready for next gen isnt doing so hott :\.The reason it seems like im posting alot of forums"i promise this will be the last"I just want this nightmare to end.Before i thought my video card was the problem ''aka 7800gt'' so i bought a 7900 to hold me down till the 8800 drop down in price or if the 8900 kills that ill roll with those.The strange thing is i get the same bs as i did with the 7800,i feel like there wasnt any difference in power.The only thing ive noticed was i went from 50-100 fps in hl2 to high 200s all the time.


My only guesses r maybe my psu isnt getting enough power to run my stuff cuz i never seen a game have black boxes on the screen before.This is ''rainbow vegas''or maybe my processor is overheating?or a batch of ram or not enough ram to run?Im so close smashing this fricking system but haha i cant it costed way to much.this is my system




video cardCI-E XFX 7900 core:600 memory clock:1600
ram :1gb ddr2 800 GEIL
psu :500watt antec smartpower 2.0
dvdr :18x dvd rw dl r
fans :2 fans in front 2 in the back including stock fan=5 fans
hdd :400gb
cessor :intel duo 6400
mobo :gigabyte 965p-ds
internet :8mb of speed

my video card has the latest drivers.
my motherboard is updated too
this is where im clueless
my games r fully updated too