PC hacked through a gift!!

[FilOnline]

Yesterday i bought the game "H1Z1" using a site (Gi Two A) which provides game keys offers from other users of steam. From the moment i accepted the gift (by a british "vendor") and installed the game my computer started to crash every 5 seconds (to open a simple folder took 10 minutes), now i'm using my tablet to write this.
In addition when i tried to open the game steam said "the game is already running".
I'm very very angry right now, my computer is evaluated over 1200 $ and i can't afford to buy a new one (I am unemployed and still searching for work..).
Now my computer is by the technical but i have a simple question:
Since it's not possible to contact directly the Steam Support, i was wondering if there is a way to delete the game by my steam library (i've already blocked and removed by my friend, the alleged hacker that does not even have an official steam profile).

Please help me if you can, i'll really appreciate it. :)

P.S: Sorry for my basic english but it is not my native language

[76561193916449244]

A key cannot hack your PC. If you redeemed the key on Steam, any downloads went through Steam. It would be different if you downloaded any software from your former friend or the web site you bought from.

The easiest way to resolve the "game is already running" error is to open Task Manager, find the game, and end the process. Or log off Windows. Or restart your PC.

On that note. Take a minute and download and update Malware Bytes:
https://www.malwarebytes.org/

Restart your PC in safe mode, and do a full scan of your computer. Honestly, it sounds like your computer is slow to respond because the game is running in the background, but it doesn't hurt to check for malware.

[Pcnuttie]

Go in safe mode and use malwarebytes and scan for viruses. And change your steam password in case. If all goes well then you should be fine. Last resort is just reformat your PC.

[crunchyfrog]

As others have stated, you CANNOT get viruses from a key (although I'd urge you not to use unofficialy sites llike that you mentioned).

But you do need to carry your disinfecting out EXACTLY as I state here. It's not just a case of downloading Malwarebytes. If you don't carry these steps out precisely, you stand chance of getting nowhere fast, as your account will still be compromised.

(1) Run your antivirus suite's INTENSIVE scan, in Windows safe mode if you can. Let it run (it will take some time, maybe 40 minutes or more) and remove any rubbish. Reboot. Run it again and if it removes nothing further, proceed to step (2). If it does remove further stuff, reboot and do it again.
(2) Download and run Mallwarebytes' Antimalware. Let it run and remove any rubbish. Reboot when it's finished and run it again. If it removes nothing further, go to step (3). If not, reboot and do it again.
(3) ONLY NOW should you change your passwords to your associated email address and your Steam account.
(4) Tell everyone on your friends list that you've been infected and to look out for bogus links from you. If they've clicked on them, send them here.

Lastly, to repeat, you MUST DO THESE STEPS PRECISELY IN ORDER or changing your passwords will serve no purpose. If there's mallware left, you'll just tell the scammer your new details.

[FilOnline]

Thank you all for the answers, but apparently i have not explained well enough.
My computer will be restored (reformat) in these days, and i wanted to know if when the PC will return (Like New) there is still the danger of running into this problem when i'll reinstall the game that can be the cause of my PC's crash (H1Z1), because the game is a gift by the alleged hacker... So I thought that the only way to prevent this is to completely remove the game from the library because I will have to reinstall all my steam games.

[Muppet among Puppets]

If its in steam, it doesnt infect you.