Fl is a massive program, what matters most is the processor. Get a good processor with more than 2 cores. Most people in the music industry choose Mac for this reason. However, the problem there is you won't be able to send and receive mp3s as well and you will end up purchasing everything. I run an Alienware 17. If you want portable and music production you are gonna spend for it. I love my laptop. Worth every penny. I also run a ssd for performance only and use the 750 gig for storage. Memory is the second most important part for music production. Go as big as you can afford with the memory, bigger workspace helps for multiplayer tracks. Finally a great sound card. So, if you want a PC start by looking at gaming computers. Alienware is fantastic. I have a friend who uses an older xps and does well. for laptops Mac owns the music industry but I think ios7 will change that. that minimum requirement, get as far ahead of that as possible. When you start recording you'll see why. Things Live reverb, acoustic instrument synthesizers and Daley effects will eat that memory up and challenge your processor. 

Also, get a copy of Magix music maker, it will keep you motivated while your learning FL. Good luck