Answer to: Intel iMac 20'' to 27'' housing upgrade?For all of the hassle and time and frustration, just find a USB to HDMI adapter and by a larger monitor. The adapter is about $60 US and a new 1080p 27" monitor can be had for under $300.
Answer to: Rattling noise left side when hard drive is running at high speedI always tell folks to grab a copy of Carbon Copy Cloner and do a block level clone of you HDD onto an external HDD via Firewire or USB. Always have a back up. I have to agree with the poster above on doing a good clean out with some canned air and replacing the fan. It's a cheap fix and shouldn't hurt. My question for you is the HDD a 5400 or 7200 drive? Make sure the screws are secure on the drive mounts and if one is loose, use a bit (sparingly!) of loc-tite on the screw to help hold it in place.