How to Make Niko Wear Claude from GTA 3's Clothes in GTA 4

Play the game until you've done several missions for Playboy X and Dwayne Forge (separately) The Last Mission involving them before what you need is Dwayne's Undress to kill mission.

Wait until X calls you for a mission and asks you to kill Dwayne. You may have to do more missions first.

Do a few missions until Dwayne calls you and asks you to kill Playboy.

Do a few more missions, until Playboy calls to ask if Dwayne is dead.

Go to the X, when you see an X and a D on your map/radar.

Chase down playboy and perform an execution.

Get a call from Dwayne.

Go to your new safe house.

Change your clothes.

Find that you have a new outfit...

Save the game

Enjoy.