I used it when i was unable to finish the elevator part in Grim Fandango (i know there is a patch for this , but my internet connectins wasnt working basck then ) because to computer was too fast , small programs with a user friendly interface , double click turbo.exe , set the % you want , keep the program open and go to your game , when you want your computer at top speed just exit the program
ftp://ftp.infogrames.net/patches/general/turbo.exe
thx to www.tweakxp.com for the link