GTA IV was released for the PC on the 3rd December this year.
Just a word of warning for those who don't have it on the PC - wait until the first patch is released until you buy it. Currently, there are several issues which need addressing.
A few irritations I've come across so far:
- You MUST be signed into Windows for Games - Live to be able to save even single player games. Not signed in = no saving the game
- The master servers for the Rockstar Social Club application are reguarly down, stopping you from playing MP
- Windows for Games - Live cannot currently be auto-updated to a bug
- Signing into the Rockstar Social Club crashes the game on launch if the master servers are experiencing issues
So, not a good start. Hopefully, the first patch will fix the issues.