My computer specs says it has a 200 GB hard drive. I want to do a complete system backup, all files, folders, everything. What is the suggestion to use for backup? USB flash, external hard drive?

External hard drive is good but you do have to remember that hard drives to go 'bad', not to say this is something that will happen or look forward to but something to keep in back of your mind

I would back up system to an external drive and also back up to DVD's also so you have 2 backups on 2 different media type