Often you can get to HDD and RAM bays without voiding warranty. Especially in those huge 17" ones.
An ultrabook you probably will void warranty though.
Just remove the 5200rpm one while you're at it and start with a fresh install. The shit they put on laptop's these days is horrible.
Else before playing any SC2 game online, just run the arcade map "Preloader" which preloads every animation and texture into your ram cache. That way it's only the initial load of sc2 and that arcade map. no jitter or slow loading once you've decided to 1v1.
my asus EEEbox has a 5400RPM drive in it, pretty sure I remember seeing that I could take it out, put in another hard drive, and be all good warranty wise so long as the new hard drive wasn't the cause of failure should anything else go wrong.
Isn't that how apple's warranty thing works too? I see a few people put SSD's into macbook pros.