I've spent countless hours searching for fixes from various issues on 8.1 from the 'nothing happening' after clicking Play and the black screen, and then stuck on loading. There is lots of threads so i thought i'd post a fresh thread with how i managed to get it working, multiplayer and everything...

1. Install GTA IV from Steam as normal.

2. Try to launch the game, copy the serial, and let it install its dependencies (WLFG, SecuROM, etc..).. once complete it will bring up social club.

3. Create an account for social club then login.. from this point it should be failing to work? If so, read on...

4. Go to Programs & Features and uninstall any Windows Live for Games Redistributable's

5. Install the following redistributable: http://go.microsoft.com/fwlink/?LinkID=201134

6. Go to http://www.xbox.com/en-US/live and login with your gamer id / windows live ID. it will ask you to accept new terms.

7. Restart

8. Launch windows live gaming app and login with your gamer id / windows live id

9. Go to C:\Program Files (x86)\Steam\SteamApps\common\Grand Theft Auto IV\GTAIV\

10. Right click GTAIV.exe, go to properties and click on Compatibility

11. Tick 'Run this program in compatibility mode for:" and change it to Windows 7.
(maybe do gta4Browser.exe and gtaEncoder.exe for good measure I've not extensive tested yet)

12. Back to steam try to launch the game again, it should bring up Social Club, login again if need be and click Play..

13. The game should now load.

I reverted my install and went through this again to verify and it definitely worked for me, hope it works for you