There is a known issue with USB connected "non bootable" devices such as a printer causing slow bootup, but not blue screens. 

 

There is an option in many Dell's (You didn't include your PC model so I can't say about yours) to set the USB to "No Boot" and that eliminates slow boot up's. 

 

As far as the blue screen, it could be a bad driver install???  Have you tried uninstalling the Canon?  Or if you have Windows ME, XP or Vista you could use the "System Restore" function and restore the PC to a date PRIOR to installing the Canon.  If that eliminates the blue screen then do a new install of the Canon (check the Canon site for any updated drivers for your Operating System and if there is, use them) and remember to ONLY physically connect the unit to the PC when the Install program tells you, DO NOT connect the unit to the PC firs.