You may have a conflict with some of the startup crap Windows comes with or variables that install themselves when you add a new program/update an existing one. Two things you can do- Look in your 'Startup Folder' Start-->Programs that start when Windows start...most of the time you can safetly delete anything there thats unused. -or- Start-->Run. Type Msconfig This will bring up a little utility within Windows, hit the startup tab if the Divx player is one of the checked boxes, uncheck it and retart system...you can always run msconfig again and check the box. Worst comes to worst, you can always roll back the XP :)