Depending on which component(s) installed the hardware profile and/or the user account may be "corrupted", so Pro Tools is unable to run on them. To create a new profile/account for Pro Tools:1) Create a new user account with administrator rights, then Log-in as the user created above and launch Pro Tools.If the problem still exists:2) Reinstall Service Pack 3 (be sure not to overwrite the new installed system drivers/components; you'll be prompted if any different components is/are detected by the service pack installation)3) Reinstall Pro Tools (you do not need to remove the "old" version)4) Restart the CPU.You'll have to reauthorize the installed Plug-Ins during the launch of Pro Tools (this does not affect any key count on the authorizer disks).