I found this in the steam forum.......................HALFLIFE-Platinum error Fix WHO EVER NEEDS HELP ON THIS ERROR OK LISTEN UP REAL CAREFULLY! OK go to your start menu and click on run And insert this regedit Next you will see 5 folders on the left look for hlkey_local_machine ok now you open. now choose the folder called software you will see a bunch of files look for the file named valve it should open up a folder named steam next, it will say default, installpath , rate delete the install path next, exit out of steam and re log in it will ask you for your cd key put in your cd key and than exit your steam and if that doesent work you have to keep opening and exiting until it asks you for your cd key again when it asks for your second time you have to put in your cd key twice (!WHEN I SAY TWICE PUT IN UR CD KEY TWICE IN A ROW DO NOT SPACE IT JUS TYPE IT IN TWICE and than hit ok and it should work.

^^^^ did this lots of times and still hasnt asked me for my cd key and now i cant find any servers???

check your filters.......but if that doesnt work........just play on our server. Its the best afterall anyway.

yeah i've tried adding the server manually but it still didnt show up

i read what u said.. i did what u said.. and i still get the error that my HL platinum pack is invalid nad my cdkey is already registered.. when i click on the server it opens up to the enter cdkey thing i put it in and it doesn the thing after that i click on the server it does this loading thing and then i get the message again.. whats going on??