I'm making this topic in case someone runs into the same problem as I did.
Being the only game in the serie I have not played yet, I bought Contracts and unfortunately, the game would not launch. Actually, a black 1024*768 sqaure would pop up for half a second after launching the .exe and that would be it.
So, I fiddled around the files and managed to get the game working in 1080p and all that jazz.

Here's what to do:
1. Open up HitmanContracts.ini (located in the game's root folder, typically C:\GOG Games\Hitman - Contracts)
2. Change both "Resolution 1024x768" lines to "Resolution [Native width]x[Native height]" (ex: "Resolution 1920x1080").
3. Change "StartUpperPos 2,2" to "StartUpperPos 0,0"
And that's it.
Also, run as Admin and with compatibility for Windows XP SP2 (should be on by default).

Hope this'll help someone out there.

You helped me fix my game not launching after changing the resolution. Thank you.

Does anybody know what this is? I am playing hitman contracts on Windows XP, and the games graphics glitch out of control, they flicker this rainbow color and I can see 47’s character model t losing. GOG will not allow me to show what I mean through video or photo for some reason though. Just look up on YouTube “what is going on with Hitman - Contracts (graphical glitch, or bug?)” to see my video on what I’m talking about. Can someone help me? I have no idea what’s going on. None of my other games have this problem, all other hitman games work fine on my laptop:

I have a core I seven CPU

I am running on AMD Firepro M6000 GPU @2.7Ghz (8 CPUs)

I have 3.22 GB of RAM

I am running DirectX9

I am using IDT Audio at full acceleration

I am running Windows XP Pro SP3 (5.1, build 2600)

I am running on a Dell Precision m6700 Mobile Workstation Laptop at 1920x1080p with 60 Hz refresh rate.

My chip type is an ATI Display adapter.