2 Questions regarding lagging an screen creaking

Hi guys, I've had my Unibody Macbook Pro since November and have 2 questions that someone may be able to help me with.

1. When my computer is plugged into it's power source, everything runs smoothly, but when it's not charging some things seem sluggish. For example when I plug in my laptop and click "Applications" on the dock it opens very smooth and quickly, and sluggish/laggish while unplugged. Could this be a battery problem?

2. Another question I have is about the black plastic underneath where it says "Macbook Pro" that is connected to the bottom aluminum. I believe it's the clutch, just to the left of the power button. Whenever I open/close the lid it creaks VERY loudly and when I touch that plastic part I get a similar sound. There is no problem with the closing itself, nor is there any clicking or cracking. I brought it to an Apple Store and they told me that there is nothing wrong, but it never made that noise for about the first 2 months. Anyone know what the problem is there?

1. Sounds like you have some setting for when you are running on battery that are causing this. I would imagine you've set the hard drive to spin down after a minute or when not plugged in and maybe have the thing set to never spin down when plugged in. That would explain why when unplugged it seems to run slower. Its just a matter of changing the settings, but realize if you change the settings that the battery life will be shorter.

2. probably just has some dust or dirt in the hinge. Be glad if that is the only problem you have with the hinge. After about a year my has gotten so loose that it will sometimes open up from 90 degrees to as wide as it goes by the force of gravity on it.