That almost definitely means software rendering.
OpenGL games can often have problems under Windows due to poor support in Windows for OpenGL.
This is a problem also for web browsers under windows since WebGL is based on GLES2. There's a project called ANGLE that tries
to work around this by offering a wrapper layer for Windows users. Once we get GLES2 integrated into Hedgewars we can try to bundle ANGLE.
It is quite possible that when you upgraded to Windows 8 your driver was changed.
Try seeing if there is a driver from ATI w/ explicit OpenGL support.

Another possibility is the glitzy new accelerated interface in Windows 8
(AFAIK hardware accelerating of the interface in Windows 8 is non-optional) is sucking up too much of your card's resources.
Since that can't be turned off, the only option there would be to reduce the demands of Hedgewars (reduce quality slider, smaller game window size).

http://pastebin.ubuntu.com - please paste your game0.log (Should be in My Documents/Hedgewars/Logs) here so we can see what driver the game is using.

... you could also try setting up an ubuntu dual boot
http://www.ubuntu.com/download/desktop/windows-installer

I also tried some other games, wich worked perfectly. It is even possible to play HD 1080p Videos.
Here is my Log: http://pastebin.ubuntu.com/1304998/

Usually I use Ubuntu, that's why I don't really what to do... I removed the dual-boot just a few weeks ago, because this is not my main computer and I wanted to try Windows 8 with enough space (not really big HDD...)

Thanks!

Are the other games OpenGL? I bet they aren't.
0: Setting up OpenGL (using driver: windib)
0: OpenGL-- Renderer: GDI Generic
0: |----- Vendor: Microsoft Corporation
0: |----- Version: 1.1.0
0: |----- Texture Size: 1024
0: |----- Number of auxiliary buffers: 0
0: \----- Extensions:
0: GL_WIN_swap_hint GL_EXT_bgra GL_EXT_paletted_texture

That part indicates you are using software rendering. No hardware acceleration under OpenGL. Check to see if ATI has a better driver than what you got with Windows 8. Heck, see if you can get your Windows 7 driver back.

Just how small is the HD? You can run Ubuntu in very little space. Hell, you can run it on a 1 gigabyte flash drive with room to spare.
Although of course if you want to do Hedgewars builds you need a bit more space than that, and I'd suggest at least 8 gigabytes to avoid future install issues.

Juhuu, I got it to work!!

It was a bit tricky

I downloaded the driver for Windows 7/Vista from the AMD-Website and let the programm unpack everything, but stopped the installation.
Then in System settings I updated the driver manually by choosing the one I just unpacked. Windows installed it and now it runs perfectly at over 120fps

Thank you for your help!

Microsoft is focused on eliminating support for OpenGL, I think, since OpenGL apps are too cross-platform, which gets people out of Windows lock-in. This isn't just on drivers in Windows, but also in terms of things like support WebGL and CSS shader language.
Glad you got it fixed, sorry you are running Windows

No idea what you guys are talking about, bought and installed Windows 8 Pro the day of the release and have been using it ever since to play Hedgewars.

It runs flawlessly! No problems whatsoever!
Tried it with the CPU integrated Intel HD 4000 with 256MB of shared DDR3 and with the dedicated Nvidia Geforce GT 650M with 2GB of dedicated DDR3.

Really absolutely no problems were detected, getting exactly the same fps I got with Windows 7 before.

EDIT:
failed to read all the posts the 1st time around, i'm glad you got it fixed!

As you can see, the default Windows 8 driver *was* a problem for him. But we've had problems w/ Windows drivers for all versions.
http://www.grokdoc.net/index.php/Dirty_Tricks_history#OpenGL