A few things could possibly affect the sound, but I doubt the laptop as much things after the laptop.
USB speed, if it's not at least USB2 it could having trouble keeping up? Harddrive could be another longshot, I've switched over to solid state drives and found things run apps load and save much quicker/smoother. Had a Macbook Pro with 5400RPM drive and it was near unusable, now it gets daily use in the garage. RAM, this is the be all, end all, go to answer for ALL computer problems, like caps on audio gear!

If the laptop generally works ok, then I'd leave it be and look down the chain.
I'm an Apple guy and switching to their laptops for just playing files will only lighten your wallet...A LOT. Perhaps an iPad might be an option, but I'd do research on what apps you'd need for hi res playback, anything over 24-bit/96kHz won't play without a 3rd party app.
My garage setup sounds horrid right now, I need to do a speaker shuffle and delete the crappier files off the laptop. I'm mainly working in there and running tools, so it has to sound good LOUD!