AMD Sempron 3100 1GB RAM and 256 shared video.

I want to use this computer to watch movies, listen music and let visitors check their email / facebook.

I want to use it with a SONY Bravia 32 inch LCD screen and the problem is that it goes default to 1920 x 1080 and doesnt matter what resolution I use, the text its extremely tiny, as well as the webpages I open on Firefox, and if I go Ctrl + its not the propper way to do it because it gets distort because of the big ammount of zoom i need to use to make it viewable.

If I try to modify the aspect of the text and fonts, it doesnt work completely because of so many configurations I need to do.

So, I brought an 18 inch Samsung monitor turn off the pc, plug it and turn it on again and it runs perfect (the size of the text) it goes to a 1360 x 768 by default with all the text looking perfect

actually that resolution works perfect for this computer, i dont need more, so I turn on the computer with the samsung monitor pluged, and after it loads, I change the court to the SONY Bravia screen and it works perfect. 

It doesnt matter what I do, if I go to settings and save the configuration, next time I turn on the computer with the SONY Bravia pluged I have the same problem.

The text its ridicusly tiny, I mean, unreadable for most of the text in all the OS.

Any ideas of how to fix this?