So, on a whim yesterday, I pulled out a shrinkwrapped copy of GTA 4, which I had gotten from a retail store long after release on the cheap. After taking forever to install content from 2 DVDs, I emit a Lovecraftian scream of SAN loss when I find out that it doesn't want to run unless I have service pack 3 for Windows XP installed. (I tried once or twice to run it in compatibility mode to no avail.) I've not installed SP3 yet, just because I knew that some people had issues with it messing up their system, and I haven't needed it for anything yet.

However, I figure that a lot of the posts complaining about SP3 messing things up are at least 2 years old and probably a lot of them had to do with old graphics card drivers being incompatible with SP3. Probably if I update all my drivers before the install, SP 3 will be okay. My other concern is if installing SP3 might break compatibility with some older games. Finally, I don't have a full system backup, so in the unlikely event that SP3 wrecked my system, I'd have to crawl through the closet hoping to find a WinXP CD, and also pull out all the software for my graphics cards etc, and then re-update all that crap over the internet, which if that did happen would be NAARRRGGHHHHHHHH.

So, in your opinion, should I go ahead and install SP3? Or is GTA 4 just not worth it?

I've not had any troubles with SP3. I'm not sure if a system restore would eliminate SP3 (it should, in theory, if MS did their job). I would probably have to recommend installing SP3 in general because it's just better security. Any hardware issues SHOULD have been patched by now... in theory. (Just be careful about installing SP3 + a bunch of other patches. I had no trouble with SP3, but a minor update to our monitor driver nearly cost us $200 in tech support!)

You should have no problem with SP3.
And it's better for your computer's security.

Install it. Problems with it are very rare and any issues you have are likely caused by an existing issue with windows itself. But if for whatever reason it fails to update or messes up your system, yes you can use the system restore to remove it.
But installing it will enhance your security as well as system performance.

You should wait and install SP4 for GTA5.

~J

SP 2 changed the TCP/IP stack, SP3 doesn't do anything that drastic so you should be just fine.