I think the Toshiba cpu is upgradeable, but the difference will not be worth the money. I understand why you would a laptop for college, hence what I recommended you to do. That should be especially possible if you have a high school graduation party
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For desktops I am thinking unless a good deal comes around you should build your own. I started building computers around your age, so you should be more than capable. I can get a list of parts for you to buy, but just need to clear up a couple things. Is your budget $700 or $550? Do you have a monitor that you can use? Probably can get decent deals over the next couple weeks on components, since its the holidays as well. The build should be more than capable of running anything you throw at it.