GTAIV (that's Grand Theft Auto 4 for you idiots) was finally FINALLY released on the PC on December 2nd/3rd 2008. The only thing with this is, is that the final/release portion was obviously rushed (trying to get it out in time for Xmas?) and people are having major problems. This post is an effort on a couple of CTRL+ALT+INS's part to help out with information and how to use it that may help you, the frustrated idiot masses. In a way, we shouldn't call you idiots because we had the same problem. But oh well, idiots.
Shad, one of our editors, is nice enough to compile answers to questions and problems that he's run into and how to solve them and has put it together here (finally, you slow ass) for the mob that is the public. He covers things backward (from problems when running, back to problems getting it running) but that's because he's stupid. Ok, not really.
Thank you. Ok, for one thing, even if you did get it installed and running, it'll be slow as hell. It's like your computer is 3 years older than it actually is. This is a combination of many problems, but here's a few answers..
NVIDIA - Link to Beta Drivers for GTAIVhttp://www.nzone.com/object/nzone_gtaiv_downloads.htmlThese drivers are from Nvidia and helped with the overall speed of the game and how it runs.
These alone took me from a slideshow to a 20+ fps playable game and that's why I am currently enjoying the heck out of the beauty that is GTAIV.
For you ATI Users, here's yours: http://game.amd.com/us-en/drivers_catalyst.aspx
For some people, turning Graphic Settings down doesn't do squat. Leave it at 1900x1200 or turn it down to the minimal 800x600 and it runs the same. This is probably a limitation of your CPU and a bunch of other things, but let's get back to what else you CAN DO.

What? You can't even adjust the settings at all? Well here are some command-line additions that you can add too your Grand Theft Auto IV shortcut/icon to force it to do what you want (make sure you are adding these to the LaunchGTAIV.exe shortcut):
ie. add -nomemrestrict -norestrictions -novblank -percentvidmem 100 to Launchgtaiv.exe NOT gtaiv.exe, run as administrator [Vista], and your graphics options will not be limited by your amount of graphics memory. Add other parameters as desired.
Tools:
-benchmark: Runs the benchmark tool and immediately exits game.
-help: Display list of all command line options
Graphics:
-renderquality: Set the render quality of the game. (0-4)
-shadowdensity: Set the shadow density of the game. (0-16)
-texturequality: Set the texture quality of the game. (0-2)
-viewdistance: Set the view distance of the game (0-99)
-detailquality: Set the detail quality of the game. (0-99)
-novblank: Disable wait for vblank (No Vsync)
-norestrictions: Do not limit graphics settings
-width: Set width of main render window (default is 800)
-height: Set height of main render window (default is 600)
-safemode: Run the graphics in the lowest setting possible
-frameLimit: Limit frame to interval of refresh rate (ex If refreshrate is 60HZ –frameLimit 1 = Locks down to 60HZ)
-refreshrate: Set the refresh rate of main render window – Warning - Monitor must support (ex. –refreshrate 60)
-fullscreen: Force fullscreen mode
-windowed: Force windowed mode
-availablevidmem: Set amount of physical Video Memory(ex. –availablevidmem 0.9)
-percentvidmem: Percentage of video memory to make available to GTA
Audio:
-fullspecaudio: Force high-end CPU audio footprint
-minspecaudio: Force low-end CPU audio footprint
System:
-noprecache: Disable precache of resources
-nomemrestrict: Disable memory restrictions

Here is an explanation of the [very few] settings that are available in the Graphics Settings Menu, from the GTAIV Rockstar Info .DOC:
THE GRAPHIC SETTINGS OF GRAND THEFT AUTO IV PC
Most users using current PC hardware as of December 2008 are advised to use medium graphics settings. Higher settings are provided for future generations of PCs with higher specifications than are currently widely available.
Graphics settings are limited by system resources by default. 256MB video cards force minimum settings by default. If a user bypasses these safety measures using command line arguments and exceeds their system resources, the users gaming experience may be compromised.
Video Mode Resolution scaling effects water, reflections, shadows, mirrors and the visible viewable distance. The resolution settings relate to the amount of available video memory. At 2560*1600 the game will require 320MB of video memory in addition to all the memory required for content. At 800*600 the game will require 32MB of video memory in addition to the content. Medium resolution settings are recommended for most users as higher settings are only usable if there is available video memory.
Texture Quality Texture quality affects the visual quality of the content of the game. High setting for textures will require 600MB of video memory at a setting of 21 View Distance in addition to the memory taken by the Video Mode. A medium texture setting is recommended for most users.
Render Quality Render quality is the texture filter quality used on most things in the world rendering. Most people would know this as anisotropic filtering. Medium settings are recommended for most users and will provide filtering beyond what the console versions can execute.
View Distance View distance scales the distance in which different objects in the world such as building and cars are seen. Raising this option increases the distance in which high quality objects must be loaded and will increase the memory it requires. Restrictions are established to ensure the game runs optimally for most users. A setting of 22 or more will provide PC users an enhanced experience over the console versions.
Detail Distance Detail distance scales aspects of the environment that the View Distance setting does not including vegetation, trash and other moveable objects. A setting of 10 would be the equivalent to the performance on a console. This setting has little effect on memory.
Vehicle Density Vehicle density scales the traffic density of the traffic in the game. It has no effect on the mission vehicles or difficultly of the game, but can have a significant impact on CPU performance
Shadow Density Shadow Density controls the number of shadows generated for positional lights in exterior environments. These shadows are exclusive to the PC version and can have a major impact on CPU and GPU performance.
Crossfire/SLI With the latest ATI driver (8-11 series) the game supports crossfire modes (ie. 4870x2) SLI is currently unsupported. Support will be added through a future game patch as well as an updated Nvidia driver.
NOTE: Background Processes Certain background processes can have a detrimental effect on system performance when playing GTA IV, especially on systems with minimum required system memory. Users should ensure they disable their Virus scans (especially “on-access” type scans) when running the game to maximize performance.
Another problem I had was getting friggin LIVE to work. After I got the game up and running finally, I couldn't save my games (or keep track of Achievements, but that wasn't as important to me).
The problem was mainly the Firewall Ports.
I had to continually ALLOW ALL / OPEN the Firewall to get everything to flow nicely, until I collected all the ports that could possibly be used for the game, the Social Club and GFW LIVE...
LIVE Firewall/Router Ports
http://support.microsoft.com/kb/908874
Other helpful ports are:
GamesForWindowsLive
1024-5000 (udp)
DirectX/DirectPlay
2300-2400 (udp/tcp), 47624
Universal Plug n Play
1900 (udp), 2869 (tcp)
Opening these ports should help get this stuff working while not having to completely turn off your firewall/put yourself in the DMZ, but then again with all these friggin ports open, you are basically nominally protected anyway.
Social Club Problem?
.NET 3.5SP1
http://www.microsoft.com/downloads/details.aspx?FamilyID=ab99342f-5d1a-413d-8319-81da479ab0d7&displaylang=en
Getting a DD3D80 or MM10 or RMN20 error?
Well here is the page at Rockstar to find out what ALL the error codes mean (not extremely helpful, but it's a start):
http://www.rockstargames.com/support/gta4pc/GTAIV_Error_Codes_ALL_EN.html
Running Windows XP?
You'll need this:
Service Pack 3 http://www.microsoft.com/downloads/details.aspx?FamilyID=5B33B5A8-5E76-401F-BE08-1E1555D4F3D4&displaylang=en
Running Vista?
You'll need this:Service Pack 1 (32-bit)http://www.microsoft.com/downloads/details.aspx?FamilyId=B0C7136D-5EBB-413B-89C9-CB3D06D12674&displaylang=en
Service Pack 1 (64-bit)
http://www.microsoft.com/downloads/details.aspx?FamilyId=874A414B-32B2-41CC-BD8B-D71EDA5EC07C&displaylang=en
Oh, and if you're getting just a black box and then it closes? Or if you're getting a crash to desktop on trying to run the Grand Theft Auto IV Shortcut?
(Also helpful if you are seeing this)
Run the Rockstar Social Club Shortcut first (can skip logon if want) and THEN run the Grand Theft Auto IV Shortcut to launch the game.
There's more, but I can't think of them right now...
