As you said when playing a game, there are a lot of processes going on. There are some fellows here who are gamers and can tell you what their experience is with half-life 2. In any event, start with your drivers. nVidia's drivers are not all equal and sometimes, the latest are not the greatest. You might want to visit some sites that talk about drivers and performance like nVnews: http://www.nvnews.net/vbulletin/ or guru of 3d: http://forums.guru3d.com/ . This is not to put you off, but until some of the fellows who have experience with those games come on, this will allow you to read about the ups and downs of drivers and the systems they work well with or mess up. There are also some tweaking tools on those sites that can address "hidden" settings on nVidia cards that might help you get around some of the glitches you mention.

I have an eVGA 6600GT AGP, HL2 runs pretty good for me, but I do have the odd freeze now and then. Seems that HL2 plays havoc with my GPU, depending on where I am in the game, it will clock down to 2D, then up to 3D low performance, then up to 3D high performance, it's all over the freakin place!
 
In other games, I find that although a I may drop down to 500mhz on the core in menus(3D low), I'm right back up to 591(3D high-OC'ed) when I go back into the game. HL2 tosses me from 3D high to 2D low while playing the game! Time to look for another patch. ;(
 
I'm running on an older system so no BIOS upgrades left for me, but I suggest you hunt for a BIOS update for your mobo, from what I've read around the net a BIOS update for the 78xx series seems to fix a lot of problems. Chipset updates are also high on the list.
 
Depending on who made your vidcard, there may also be a BIOS update for it, I know eVGA has Bios updates for some of their 78xx series cards.
 
As for opening up the hidden settings on your card, I use NVTweak: http://downloads.guru3d.com/download.php?det=911 for those, and overclocking, and RivaTuner: http://downloads.guru3d.com/download.php?det=163 for monitoring. Only use one utility to overclock, not both at the same time. It's fine to OC with RivaTuner, provided you aren't OC'ing with NVTweak at the same time. I use NVTweak for the OC as the GUI is a lot more friendly, RivaTuner takes a bit to get used to.
 
Tons of drivers at guru3d.com too, pick a flavour. Also, after uninstalling drivers, reboot into safe mode and clean up the garbage left behind with Driver Cleaner Pro: http://majorgeeks.com/Driver_Cleaner_Professional_d3214.html reboot, then install the new drivers.
 
Hope that helps a bit.

yea ive tried all those beta drivers even old ones. I shouldnt even have to overclock my card to get the performance with half life 2.

Others are having the same problem, you just aren't finding the forums.
 
A quote from a mod in the eVGA forums, about a 7800GT CO with your prob: "Also, chech to make sure that Your Graphics Card is on its own IRQ and not sharing an IRQ with another Componant. Also, what Main Board are you using? If it is ASUS then set Your PEG Link Mode to Fast, or Fastest, and then set the PCIe Frequency to 125.MGz."
 
Hope that helps, thread can be found here: http://evga.com/community/messageboard/topic.asp?TOPIC_ID=10268
 
***EDIT*** BTW, I agree, your card should be kickin butt without OC'ing it, mine is a wee babe compared to yours, I have to OC.

ok how do i change my peg link and how do i increase pci-e settings?

You'll have to change those settings in your BIOS, usually hitting "delete" when booting up will get you into your BIOS. RTFM, it should tell you where the settings are for PEG and the PCI-E settings.
 
If you can't find it, let us know what the exact model of your mobo is, we'll hunt that info down for you.

asus sli (not deluxe)

Boot into your BIOS by holding the delete key when you bootup, chose the "Advanced" menu, for the PEG mode, select "PEG Link Mode" then select fast or fastest.
 
For the PCI-E frequency, select "Jumper free configuration/PCI Express clock", and then set it to 125.

I am having the same problems with Dark Age of Camelot and after a while I lose connections. Also in EQ2 I play along for a while and after a while it will get choppy and I will have my characters left arm disappear and then after more time it will start going to a black screen in certain positions, then I can turn and get graphics back. I bought an Asus motherboard and doing what you said seems to have fixed DAOC. My question is that if I put the evga motherboard back in is there the same setting for the ped, and if I set that will it fix there as well? I also am running amd 3800 64 X2 with evga 7800 gt card with ocz 2 gig ram 2.2 latency ram. I had the guy at the computer shop tell me that it may have been do to the quality of the motherboard by evga because the heatsinks were not even straight on the motherboard shoing some carelesness in its assembly, his words not mine. I wanted to also know should I not go back to the evga board? Thanks.

I feel your pain. I just put together an Asus Sli Premium W\ AMD 4000+ and an Asus 7800GTX. I am running a single card at present. I was really chopfallen to see the sluggish frame rates in HL2 (especially split second freezes just prior to explosions, it reminded me of Half Life on my P166 ).
 
The fix? Asus A8N motherboards are still coming with the 1008 bios. Update to the 1009 bios (if you're really feeling brave you can try the beta, but I would wait). All I can say is this is what made a big difference for me. Damn smooth now. I'm not finished messing with this thing though. I think there's alot to be found yet but I want everything to be running smooth and stable at "stock" settings before I start messing 'inside' the bios or with the graphics card (still looking for the VGA bios). So far I'm not that impressed with the nvidia NF4 chipset but I have hope.
 
Use the Asus Update tool. Download the appropriate motherboard bios to a folder and direct the update tool to there to flash. Don't bother trying to get the tool to download the bios itself. Other than that it's fool proof. Don't be intimidated by it.
 
Once again, I think it's very important that you have all the latest drivers from Asus or nVidia (chipset, graphics etc...) and an updated bios before you start messing with anything else. You shouldn't have to be resorting to tweaks to get HL2, definitely HL2, to run smooth at it's default settings. Now a game like F.E.A.R. is antoher matter, that could bog down the best of rigs.
 
Good luck!

U guys are very luckey to have a very new video card i have a video card it is 64mb but it still pretty good and my card can nearly play every single game invent. >>>>