The loading screens cycle forever but the game never reaches the "start" prompt. A texture inside playerped.rpf has a broken mipmap chain. Fix: Restore your backup.
To understand the need for a backup, one must first understand what playerped.rpf contains. Located in the Rockstar Games/Grand Theft Auto IV/pc/models/cdimages/ directory, this archive file (using Rockstar’s proprietary RenderWare binary stream format) holds all the data for Niko Bellic’s in-game representation. Unlike simple texture replacements, playerped.rpf is a complex bundle of: gta 4 playerpedrpf backup