Crash to desktop

A Crash To Desktop (or CTD) is a computer program crash which is said to occur when a program (especially a video game) unexpectedly quits, abruptly taking the user back to the desktop. Usually, the term is applied only to crashes where no error is displayed, hence all the user sees as a result of the crash is the desktop. Many times there is no apparent action that causes a CTD. During normal function, the game may freeze for a shorter period of time, and then close by itself. Also during normal function, the game may become a black screen and play the last few seconds of sound (depending on the size of the data buffer) that was being played repeatedly before it crashes to desktop. Other times it may appear to be triggered by a certain action, such as loading an area.

The CTD bugs are considered particularly problematic for users. Since they frequently display no error message, it can be very difficult to track down the source of the problem, especially if the times they occur and the actions taking place right before the CTD do not appear to have any pattern or common ground.

Causes
A CTD can happen in games of The Sims series for multiple reasons:
 * Hardware incompatibilities
 * Just barely reaching minimum requirements for the game
 * Too powerful machine (Using more than 2GB RAM)
 * Incompatible or corrupt mods/custom content
 * Corrupted data
 * Too many background applications running at the same time

Solutions
Some users have CTDs because of user-hardware incompatibilties: their machine only reaches the minimum requirements (and they have their settings too high), their machine is far too powerful (fixing this requires modding the .exe to never attempt to use more than 2gb of ram), and other less common (and more difficult to fix) hardware issues. Crashes may also be caused by incompatible mods that have been installed, or other user-software changes.

ModTheSims has created this help thread, with tips on addressing bugs that cause CTDs.