I want to file a seperate business tax and because im on the same computer it won't allow me to do so, how can i start my business taxes

You will need to go to the beginning and Start a completely new return for the business  -  if you do not want them combined with you personal tax return.

If you are self-employed your small business is included in your personal return. If you are talking about another kind of business (scorp, c-corp, partnership, etc) that kind of business uses TurboTax Business a CD/download program.

https://turbotax.intuit.com/small-business-taxes/

If you need to use the separate Turbo Tax Business program it can only be installed on a full Windows computer and not online.  But your Windows is too old.  

Window System Reqmt <a rel="nofollow" target="_blank" href="https://ttlc.intuit.com/questions/1901571-minimum-system-requirements-for-turbotax-windows-software">https://ttlc.intuit.com/questions/1901571-minimum-system-requirements-for-turbotax-windows-software</a>