How do you unlock all Sims 2 clothes on the PC?

In the Neighborhood screen, use CTRL+SHIFT+C and type in boolprop TestingCheatsEnable true and hit enter.

Then enter the Create-A-Family screen and use CTRL+N, and a dialog box will pop up notifying you that you have activated the hidden clothing, skins, and other accessories.

When you are done, use CTL+M to close these and then again in the Neighborhood screen use CTRL+SHIFT+C and type in boolprop TestingCheatsEnabled false and hit enter to deactivate the cheat.

This is an extremely powerful cheat, and leaving it running ingame (when you don't plan to use it) can cause problems with your game, and potentially cause a crash.