It should be a 6-year computer that needs a new cPU to run latest video software. Usually when software can't run, the computer needs an upgrade. The other three options would be replace. The first obviously needs to be replaced. The second would cost too much to upgrade, and would be more logical to replace if you're only needing an extra 25% cost for a brand new computer than an upgrade. The last one needs more RAM upgraded, but it's not a software issue or a software upgrade. It would be a RAM upgrade
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Have an amazing day!