Have you checked to make sure you're free of any little pests that might be sucking up crittical CPU cycles? If you use Internet Explorer regularly, then you're almost certainly infested.
Also, I know HL2 has a known stuttering problem with the gold release. It was a game bug, and it happened to everyone. Not sure if Valve has fixed it yet or not... I never really got into HL2. For other games, you might try lowering the resolution to see if that helps, along with detail levels. I know the whole reason to get a new card is to be able to run it well with full detail levels, but see if that fixes anything.
You might want to try updating your motherboard chipset drivers as well. I don't know offhand if that's a VIA chipset board or nForce, but since you said it had an integrated GF4 card, probably nForce2. So go to nVidia's site, and download their chipset drivers, not their video card drivers. It's a whole different category on their driver selector. You should have this installed regardless of what video card you're using. If it's actually a VIA chipset, then get the latest Hyperion 4-in-1 drivers from http://www.viaarena.com and install those.
I've also found that some games don't respond well to having motherboard monitoring programs running. So any sort of CPU temp monitor, should be shut down.
Finally, if you haven't already installed SP2, do so, since it includes the latest version of DirectX. You should have a card that hardware accelerates most DirectX 9 functions, but if you have DirectX 8.1 instead of 9, then the game will do all DirectX 9 stuff in software which takes a lot of CPU power.
Recently, I over-hauled my PC by replacing my awful Geforce4 MX on-board card with a new Sapphire ATI Radeon x800 Pro 256MB gfx.
Now, to assist this, I also upgraded my RAM from 512mb DDR to 1GB (512mb x 2 DDR pc2700 33mhz) and a new 460w Power Supply.
However, when I'm playing games etc, I still get stuttering when a lot of action is taking place in a game, such as Painkiller or Half Life 2. Especially when a lot of models are on screen.
I've done all the basics. I've installed the latest versions of the ATI Catalyst drivers, I've installed older versions etc. I've tried the drivers from the installation CD and I'm still getting a stuttering effect, which shouldn't be happening with the new card.
I'm also using the ATI cat-unistaller when I'm uninstalling drivers. I have uninstalled the nvidia drivers from add/remove and I also used 'Driver Cleaner' to clean any Nvidia drivers that are lurking.
Does anyone know what the problem is? Could there be a driver conflict? Could old Nvidia drivers still be lurking and causing a problem?
Also, is there an official Nvidia uninstaller ultility out there like the ATI Cat-uninstaller which gets rid of all known nvidia gfx drivers? If there is, could someone possibly send it to me or give me the URL to the file?
For the record, here is the spec of my PC:
AMD Athlon 3200+ XP processor
1GB (2 x 512MB) PC2700 333mhz DDR Dual Channel Kit RAM
ATI Radeon x800 PRO 256MB gfx.
Motherboard: Asus A7N8X-VM/400
Windows XP Home Edition
Can anyone help?
PS. If anyone does have some sort of Nvidia driver uninstaller utility could you send it to firstname.lastname@example.org
I greatly appreciate any help.