That's it... my s**tty laptop restarts aftar playing some seconds GTA IV and I'm tired, I definitelly can't play LCPD:FR anymore... This sucks, I feel sad, angry, mad... no money to buy a good PC, it's over... God...

I'm not really sure if this is a question or not, I'm sorry your computer is acting up. Have you tried using any commandlines? Try creating a file called commandline.txt in your GTA IV root directory and enter the following lines: 

-renderquality 0 -shadowdensity 0 -texturequality 0 -viewdistance 0 -detailquality 0 -novblank -norestrictions -percentvidmem 100 -minspecaudio -novsync -renderquality 0 -frameLimit 0 -nomemrestrict

Thanks for your reply, but this is not about settings, I already have a good commandline btw and I didn't changed anything on my PC, everything was fine... This problem has to do with my GPU, I f***ed it up and now can't play IV, my laptop reboots or shows like salsdjflaskdgjkjsdkf in the screen (GPU fails) after 20 seconds trying to play :(

So... you already know what's wrong? I'm not sure what good a topic could do then...