Can I use my old computer as a router for 2 internet services?

I heard there are pc programs that makes a router out of a pc.I have 3 coputers ,2 new, and 2 internet conectins, one is ADSL2 and the other is optical fiber.I don’t care what operating sistem i have to install or what i have to buy.Can i use both connections at the same time for greater speed and my old computer as a router?

yes why not u can do that