How can I fix “Display driver igfx stopped responding and has recovered” errors?

Try this:
1. In Windows Vista, go Start Menu (blue circle in lower left) => Control Panel => Check for Updates (under Security) => Change Settings => put checkmarks next to “Include recommended updates…” and “Use Microsoft Update”. Single left-click on the OK button. This will return you to the original update window.
2. Choose “Check for updates…” from the left side of the window. If potential updates are found, single left-click on “View available updates”. Mark all updates for installation, using checkmarks, then single left-click on Install. Restart your computer after all updates have been installed.
If that fails, go to the Drivers and Downloads section of http://support.dell.com/ and then enter your computer’s Service Tag. This will allow you to download updates which have been designed specifically for your computer. Due to the nature of your problem, I recommend that you install BIOS and graphics updates. Restart your computer after installing each of these updates.