Hi guys, I've seen a few of these threads but I need more information. 5400rpm HDD is a bit slower but uses less power. Exactly how much power is lost to upgrading? I know its not much but its important. The 7200rpm upgrade is like an extra 40 GBP or if I downgrade the spec to a 320gb its cheaper than the 5200rpm 500gb. If I get 4 hours of battery life on a 5400rpm, how long would a 7200rpm last? Is there a loss of an hour? or a mere 15 minutes? Thanks.