As you probably know, amending msconfig will only speed up the bootup sequence of your computer. From Windows 7 onwards, this is only a marginal, albeit useful, tweak to imporve performance as Windows 7 staggers the boot sequence to get people up and running and starting other processes later.
Further to Dr.M's advice, have a look at
ccleaner which is another powerful tool to clean up your PC. Ultimately I am a fan of the periodic intallation of the OS from scratch (obviously after backing up everything). Gives you that 'new car smell' for computers every time!!