BSOD while randomly surfing the web

Hi, i've had the first BSOD yesterday and 4 today and i think i was mostly surfing on youtube. I can't remember changing anything on my computer since then.
A few weeks ago i tried to install a couple of old games but most of them failed to start and also they tried to overwrite my DirectX 11 (and maybe the graphics driver) with some older version.

edit: added another crash dump file

I'll take a look at the dumps an see if I can find anything.

I think it crashes when i run thundebird and chrome at the same time. This has never happened before. Also i'm not sure if that's the only reason because in some crash dumps there is no chrome or thunderbird mentioned.

So far all your BSOD's occured with different processes: chome.exe, skype.exe, explorer.exe, thunderbird.exe with the same bugcheck_str 0x3b and no additional useful information in the dump files. The dump files only give you some glues to analyze the crashes so in this case it leads me to believe that one of your memory stick is bad. Please download Memtest86+ - Advanced Memory Diagnostic Tool, burn it to a CD/USB stick then boot up your PC from CD/USB. Let it run for at least 3 passes but preferably to let it run over night.

BTW, if you have installed any 3rd party anti virus software, please uninstall it first

Please report back if you find anything. Good luck !!!