After installing Grand Theft Auto IV and adding the 1.0.3.0 Patch the game would not start. It took me about 4 hours to resolve all this errors.

The first error I got was easy to resolve. SecuROM doesn't like Prozess Explorer. So I did a reboot without starting Process Explorer and the SecuROM error 5024 was gone.
http://www.securom.com/message.asp?m=module&c=5024

Then I got an error from Games for Windows – LIVE which could be resolved by installing the Windows XP KB938759 Hotfix.

The third error was the most tricky to resolve.
I don't really know why it works now, here is what I did:

• I uninstalled ALL .NET Framework versions and rebooted as required
• I downloaded and installed .NET Framework and Hotfixes in the following order:
• dotnetfx35.exe - .NET Framework 3.5 (probably this can be skipped?)
• dotnetfx35sp1.exe – SP1 for .NET 3.5
• NDP20SP2-KB958481-x86.exe – SP2 for .NET 2.0
• NDP30SP2-KB958483-x86.exe – SP2 for .NET 3.0
• NDP35SP1-KB958484-x86.exe – SP1 for .NET 3.5
• I reinstalled GTA IV Patch 1.0.3.0. I don't know why, but GTAIV.exe was still version 1.0.0.0
• The game starts!