To be honest I have no idea if YUV is equal to Prores. FC doesn’t use or needs more than 4GB of RAM. Of course I would recomend you to use the better computer but since you don’t have Premiere or Avid on the PC I think you are stuck with Mac. There’s trials of bot programs I think but if you are going to edit for a long period of time i would not recomend it.
There are also monthly fees for the use of Premiere so that maybe an option for you.
what’s your final destination? DVD, Web, cinema?
But no matter what you do I would recomend that you put all your media on a different drive than your OS HDD. A disk with firewire 800 will do the trick.