I haven't tried it on TF2, CS 1.6 or HL2. I wouldn't know about it. :/
This problem can take it away on Steam, not "No Steam" version.
(Sorry for the black bars or the outdated resolution)
You might wonder why does this problem appear? Well, I have no idea. Since I played a zombies mod on an old PC, I didn't have any issue. But now I own a new CPU, this error message popped up somewhere. I don't know...but I hope this solution can play it without an issue.
Thumbs up if it works for you and...thumbs down if it doesn't work.
*Where can I find my real IP?:
You can find out on www.whatismyip.com and then type your IP on next to +clientport. (I mispelled +clienport in the video)
Example: The IP could be like 271.111.999.666 (It should have 4 dots. This one I just projected it. It's not real.)
1) If the steps I did didn't work, try to go to Control Panel then System and security and then "Allow a program through windows firewall"* near of Windows Firewall (click Change settings if you can't tick or untick the programs), see if there's a program called "Team Fortress 2" and to the left, tick it.
I'd like to know about you if it did work or did not work.
One thing, don't erase all the details I did on the video "+clientport..." in Set Launch Options, if it works, as well.
The "...-console" in Set Launch Options is just to open the console in the game. I couldn't open the console with my ° or | symbol in my keyboard.
*If you can't open the "Allow a program through..." neither "Windows Firewall", go to this link http://www.tweaking.com/content/page/windows_repair_all_in_one.html
You can download it on Portable, if you want to.
Once you've downloaded it, open Repair_Windows (application).
Before you repair your program, I'd suggest you to do a backup.
Go to the Backup tap, click "Backup". Let the computer process its backup registry.
Now, head over Repairs tab, it'll pop up a new window of Tweaking.com.
Click "unselect all", mark/tick one empty box of "06 - Repair Windows Firewall" and click "Start Repairs".
Once it's repaired alone, it'll ask you to restart the computer, accept it. So, it'll restart it. See if you can now open "Allow a program through Windows Firewall".
2) Here's another solution by Jonas Pedersen:
He went ''to my Norton.Next to Security and allowed my HL2 Throw My Internet Connection. Found out 100% Myself ''.
3) For those who don't have Steam, here's a theory I have:
If CSS doesn't start (Steam says Launching Counter-Strike: Source and nothing comes up), try this method I found by iPlayer on Steam forum:
1. Open your root CSS folder
2. Create steam_appid.txt and write "240" (without quotes) in it
3. Launch hl2.exe with these options:
+clientport xxx.xxx.xxx.xxx -game cstrike -console -steam
4. And try to join the server that won't let you join.
For those people who have negative responses because this video didn't solve your serious problem,
I'm very sorry. I can't please everyone and you're not happy with this video I made. You might imagine you want me to kill me but it doesn't solve the problem, either. But, again, if you rant me, you're poisoning yourself.