HDD Replacing.

the main bottle neck in modern computers is the read/write speeds of the HDD.

if your 320gb drive is a 7200rpm drive.... and your 1TB drive is 5900rpm, you will notice a MAJOR performance decrease in alot of tasks!

-Opening Apps

-Copying Files

-I can't think of any more!

Think carefully, I have a 2TB 7,200rpm HDD and it is a major bottleneck!!!! I want a SSD so bad!

 

Besides what was said above about the disk I/O speed holding things back (which I wholeheartedly agree with), also of note is that Intel iMacs are a pain in the rear to disassemble. They use Torx screws as well as several other non-standard fasteners.

 

I have just replaced my 24" iMac mid-2007 internal HDD with an OCZ 120Gb 3.5" SSD today using the guide on http://www.ifixit.com/Browse/iMac_Intel - they tend to only do a guide for the smaller screen size of each year's model of iMac, so check there for a HDD replacement guide. Most of the details will be the same for the larger size except possibly some bezel screw sizes and possibly the LCD inverter cable.

You should be fine with a Western Digital Caviar Blue 7200rpm drive in your chosen capacity.

As for tools, grab yourself the torx tool set that tends to appear on eBay for about £5 / $8 - I only used the T6 and T8 bits. Suction cups can be got from any poundshop and I bought two of the sort to put tea-towels onto the wall for 0.70p each. The main issue with the installation was actually the dust when refitting the LCD but a good clean while the case was in bits and taking care not to get any fingerprints on the screen worked. A wipe with a clean microfibre cloth and all was well.