Hi Raymo,
Looks like your getting a little frustrated there.
But hang in there
it will get better if you put the time in on the PC.
I use an unmodded Canon 1100D too, and you can get good results.
As Fred stated you need to install the software for your camera called (EOS Utility).
As for myself, I convert raws into 16 bit tiffs, which is handled by (digital photo professional) again software that comes with the camera.
Although I can use raws in the 3.3 version of Deep Sky stacker, I have far more success with tiffs.
Again personal preference and the way I process.
Don't forget to convert all dark, flat and bias frames to 16 bit tiff too.
DSS won't have any problems reading these.
Now for DSS.
You will see in the menu on the left Options - settings.
Go to settings.
Stacking settings.
Result.
Select standard mode.
Then go to ( light ) and select median.
Repeat this option for darks and flat frames.
Again in options - settings, go register settings and set to around 30%.
This setting will take less time for each frame to register. You need to set it to around 5% when there's less stars in the frame otherwise the frames won't register properly.
You may already know what I've just outlined, but worth mentioning and there should be no problem stacking your images.
These are probably the most basic settings in DSS.
If everything has worked and the images stacked successfully, it's time to save your image.
Under processing - Save picture to file, select ( Embed adjustments in the saved image but do not apply them ). Save as 16 bit tiff, file name of your preference. Select to save to your desk top initially, that way the image won't get lost.
I prefer this setting as DSS is a little slow to do anything else but the stacking procedure, you can do that in Photo Shop are what ever processing program you are using.
Note this is the way I do it, there are many others, but this way works!
But as I said earlier, you need to put the time in on the PC, and read any help files available and experiment and it will get better.
If you do have more problems, PM me and I'll try and help.
Cheers,
Justin.