If this is when you boot up it looks like some startup file is attempting to load something that is no longer installed.

Have you uninstalled anything recently, or removed any viruses or other malware?

If so, have a look at MSCONFIG, (Start > Run, type in msconfig then click OK), then the Startup tab, and check down the list for anything that looks out of place. if you find anything, remove the tick, click Apply/OK, then reboot.