IE6 is set up to resize the images based on the Display DPI setting. Dell ships its Inspirons with higher DPI than the default and sets IE6 to resize the image.

You can either set the DPI to the default (Normal - 96) or remove IE6's UseHR registry key to deactivate image resizing. Here are the relevant information (from Microsoft Knowledge Base):

Image Scaling in Internet Explorer (hi-res)

How to Activate Image Scaling
Internet Explorer 6 and later automatically adjusts the scale on higher resolution systems when the DPI setting is higher than 96 DPI and the "UseHR" registry value is added to the registry. These are usually done by the manufacturers of higher resolution systems.

Set the DPI
These are the steps for changing the DPI setting on your system.

Right-click the Windows desktop to display the context menu.
Click Properties on the context menu to display the Display Properties dialog.
Click the Settings tab on the Display Properties dialog to display the Settings tab.
Click the Advanced button on the Settings tab to display the monitor properties dialog.
Select a DPI setting in the Display frame of the monitor properties dialog to change the DPI setting.
Restart your system to allow the changes to take effect.
Add the UseHR Registry Entry
The UseHR value is added to the Main key under "Internet Explorer" as follows:

HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
Right Click in the right pane and select New>DWORD value and set its data to 00000001

This problem can also be caused by bad video drivers. Update your drivers from the manufacturers site.