Yet a new problem! [Need Help]

[[eVo]Rizla]

have you tried a 32bit OS?

[KmanN]

have you tried a 32bit OS?

Nub! he has over 3.5gb of ram so 32bit os would be stupid.

try like GPU-Z and see if its using the gpu's processor and ram while playing tf2.

[[eVo]Rizla]

why is ruling out 64bit OS stupid?

[[V]ACE]

why is ruling out 64bit OS stupid?

Didn't he have 32bit os originally and it lagged?

Good news about lfd2...strange about ft2. Have you tried lowering all the settings to minimum and see if it lags? If it does it could rule the gfx card out. If it still lags then it not the card but something else (we are starting to run out of things to blame D:)

BTW you read the reply on the tech guys forum?

[Faraday]

Originally I had 32-bit. But it caused the lag issue and so I installed 64-bit.
I read the reply on Tech Guy Forums, but I don't think that guy knows something more.

This is what I get so far, it's not my PSU (tested at the shop), it's not the GPU (tested with my old GPU), it's not the OS, it's not Steam...

I'm gonna try turning off the cool 'n quiet option and see what it tells me. I've given up for lik 80% on the matter, and I'm on my way of saving up for some new gear.

[EnzoMortelli]

Try to run ur progs on high settings (u could even give highest settings a chance).
Some systems have big problems (like mine) to make some games work properly on low settings, but run them fine on max settings.

[Faraday]

Already tried in different resolutions, different quality settings, etc...
The thing that strikes me is that L4D2 works great, but TF2 doesn't, even though it works on the same engine. I'm starting to think that TF2 doesn't fully support my GPU (since it's a brand new type). When I launch L4D2 it gives me a pop-up saying that my GPU isn't in their database and it asks me to upload the details. TF2 doesn't do this but it gives horrible lag.

[[eVo]Rizla]

do u have an old card to test with?

[[V]ACE]

This may or may not help but anyways:
On nvidia website it gives you "profiles" for games to download (to improve graphics performance) Its got L4D on there - i have not tried this but thought it might help you out with some games (tf2 aint on there)
http://uk.geforce.com/optimise/optimal-game-settings/gpu-GeForce-GTX-550-Ti

AN IDEA: though im sure this has been suggested.
If you kept your old 9600gt then uninstall all nvidia stuff, and reinstall that card and try TF2 - if it lags then its not the gfx card.
You can optimize settings for games in the "nvidia control panel" (right click your desktop, click it) Go in to "manage 3d settings, click on program settings tab, look for tf2 or click "add" and find the game. Then try to fiddle with those settings (i would say start on low/off then see if that helps).