Many new laptops (such as the Dell Latitude D600) have high resolution, 120 dpi (dots per inch) screens. Historically most PC's and laptops have 96 dpi screens.
The dpi can be switched between 120 and 96 dpi (and perhaps other values) by:
Right click on the desktop, display properties -> settings -> advanced, select the desired dpi (reboot required)
Note that this does not affect the size or resolution of the display, it simply tells XP and applications the relationship between the pixel size and "real" inches. Many programs use this information so that fonts and images are rendered at the correct size. For example, Microsoft Office applications and the XP Desktop use larger fonts so that objects appear the same absolute size they would on a 96 dpi monitor.
Microsoft Internet Explorer will scale (enlarge) web pages when the dpi is set to high resolution (120 dpi) if a certain flag is set in the registry. If your laptop has a high-resolution screen this flag has probably been set at the factory.
However, scaling images in an Internet browser is problematic, since most web-oriented images are designed in terms of pixels, not in terms of inches or centimeters. Scaling a typical "gif" image for the 120 dpi setting makes it appear choppy and grainy. Even worse, many so-called ActiveX Controls do not scale properly. For example, when performing Windows Update a pop-up box asks you to confirm that you want to install the bug fixes. This pop-up box is created such a buggy ActiveX control, with the effect that the "accept" button is cropped away: you cannot do an update!
There are two possible solutions:
You can read Microsoft's information here.