hi ArMc, this is probably caused by microsoft update kb3013455 which can cause font rendering issues on vista: <blockquote>After you install security update 3013455, you may notice some text quality degradation in certain scenarios. The problem only occurs on systems that are running Windows Vista SP2 or Windows Server 2003 SP2. Microsoft is researching this problem and will post more information in this article when the information becomes available. </blockquote> ^{reference: https://support.microsoft.com/kb/3013455} one option may be to [http://windows.microsoft.com/en-us/windows/remove-update#1TC=windows-vista roll-back this particular update] for now until there is a fix by microsoft or you could also look if there is a [[Upgrade your graphics drivers to use hardware acceleration and WebGL|graphics driver update]] available on the website of the vendor (intel/amd/nvidia) which might also resolve this problem in some cases.

Thanks Philipp, I unistalled the update and the text is now displayed normally.