Uh, well your computer is not adequete for SMP Folding, but you sure can do the normal one ment for lower end systems, they should only take 3-5 days on that computer, if you let it go all the time. And you can let it go during computer use as well. It will simply dedicate less CPU cycles to folding when your gamming or what not.
Now I know you computer does not compare to mine in any way BUT, when I was stable at 3.303 Ghz, I could play surpeme commander On MAX settings with well over 2000 units on the map at once while SMP Folding was running... (Farcry on max settings to, all games 1440 by 900)