I'm running a very similar Acer Aspire with AMD 64 bit processor and widescreen but different graphics card. I get correct web rendering in IE, Firefox, Opera and Avant. That makes me suspect the settings for the graphics card.
Howevr what screen resolution was the previous computer? When you go from 1078*650 to 1280*800 the font is much smaller, and maybe what you have is correct but you just don't like it.
I routinely use Opera as my browser and mail client. It has lots of features, such as increasing font size is achieved by pressing + (and - reduces font size). Plus you can set font style and size for almost all functions.