Clemens,
In order to troubleshoot your problem we need to know more detailed specs of your system hardware.
1. Go to Start > Run, and type msinfo32. then expand the Conmponents tree and choose a device
2. Go to Control Panel > Device Manager and look for any entry that has a yellow flag beside it.
3. Download
System Information Viwer
4. Download
PC WIZARD 2008
5 Please fill out your computers specs in the User Control Panel here on the site as well. It will then appear next to your name. look at my posting and you'll see the drop-down arrow.