I would try and launch the game with the -autoconfig switch. Instructions here: https://support.steampowered.com/kb_article.php?ref=1040-JWMT-2947

 

Thanks, I'll go on that.

 

umm, I did the -autoconfig command but it the problem still remains. Also, how do I 'undo' a command, like
'-windowed or -sw'?

 

did you uninstall TF2 or did you uninstall steam? Re-installing steam can sometimes solve this, but before you do that try using other launch options, such as -dxlevel 80

 

Alright, I uninstalled TF2, not steam, because I dont want to lose my items, but if I have to, I will.

EDIT: A month ago, it was fine, working perfectly, but now it won't run.

 

If you have to uninstall steam (I hate it when I got to do that), make a backup of your steamapps folder so you do not need to re-download games. I would hate it if I had to do another re-install of steam, there goes 100GB+ of games :O

 

Yeah, seems like I'll have to re-install steam . What about my items on TF2 and whatnot?

 

It sucks when you have to do that. Your TF2 items will still be there, it has cloud support, so your settings, achievements and items is saved on the steam database.

 

Okay,
So all I have to do is re-install steam, and download tf2? (Thats the main game I play, I also have l4d, portal and css.)

And all my items are cloud-supported, so its saved on the steam cloud database?
Thanks alot, its solved.

 

Yes do that. Only Source games (TF2, CSS, HL2 etc) have cloud support. And yes it is saved on the database. If you would like to play source games with me sometime, send me a PM and I'll play some